user48180: My project is an Arduino-based device, packed into a box.
It will need to use Speed, Latitude, Longitude and Altitude data to log hills it detects on to an SD. On the press of a button, it will need to upload the hill data to the server via Wi-Fi.
I need the following items:

GPS Module + Antenna
WiFi Module
SD Module
Altimeter
microSD Card
Inline switch for my battery pack

The cost? Well on the Pi Hut it was £120 or so:

GPS =
  https://thepihut.com/products/sim808-gps-gprs-gsm-shield-for-arduino =
  £42
WiFi =
  https://thepihut.com/products/wifi-shield-v3-for-arduino-rpsma-802-11b-g-n
  = £54
SD = https://thepihut.com/products/microsd-card-module-for-arduino =
  £6
microSD Card = https://thepihut.com/products/blank-micro-sd-cards
  (4GB) = £5
Altimeter =
  https://thepihut.com/products/adafruit-bmp280-i2c-or-spi-barometric-pressure-altitude-sensor
  = £10
Switch =
  https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack
  = £2.50

On Bang Good (a really cheap online shop I discovered) it was more like £30:

GPS = 
  https://www.banggood.com/GPS-UBLOX-NEO-7N-Satellite-Positioning-Module-For-Arduino-51MCU-STM32-p-1203610.html?rmmds=cart_middle_products&cur_warehouse=CN
  = £10.54
GPS Antenna = 
  https://www.banggood.com/GPS-Active-Ceramic-Antenna-IPX-IPEX-Interface-For-GPS-Module-p-1203537.html?rmmds=cart_middle_products&cur_warehouse=CN 
  = £2.11
WiFi = https://www.banggood.com/Upgraded-Version-1M-Flash-ESP8266-ESP-01-WIFI-Transceiver-Wireless-Module-p-979509.html?rmmds=cart_middle_products
  = £2.53
SD = https://www.banggood.com/Micro-SD-TF-Card-Memory-Shield-Module-SPI-Mciro-SD-Adapter-For-Arduino-p-919914.html?rmmds=cart_middle_products&cur_warehouse=CN
  = £1.02
microSD Card = https://www.banggood.com/4GB-MicroSD-Card-with-Card-Reader-for-RC-FPV-Camera-Quadcopter-p-1050069.html?rmmds=cart_middle_products&cur_warehouse=CN
  = £3.96
Altimeter = https://www.banggood.com/MPL3115A2-IIC-I2C-Intelligent-Temperature-Pressure-Altitude-Sensor-V2_0-For-Arduino-p-1198222.html?rmmds=cart_middle_products
  = £5.16
Switch = https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack
= £2.50 (From Pi Hut, though)

I'm suspicious. I might be inexperienced, and this may be a bad question, but is the cheaper option lower in quality? Is the expensive one over the top? The cheap version really seems to good to be true.

user6936: The main reason that some devices on eBay, or where ever, are markedly cheaper is that they are clones produced by a third party, using designs that have been copied/pirated or reverse engineered.
This reduces the third party's set up costs, quality assurance (QA) (i.e. testing) costs and research and development (R&D) costs to almost zero (compared to those of the original manufacturer).
So, generally, the board will, for all intents and purposes, be the same physically, just at a much lower cost, and, as dandavis states in his comment, probably with the same reliability and quality. 
However, if you purchase these clones, then the research and development aren't being paid for and may inhibit further growth in the market.
In addition, sometimes the cost is reduced even further as the third party cloner will use inferior and cheaper, alternative, components which may cause the device to fail sooner than the original. They may even come from the same factory and be devices that are using the original components, but which have failed the QA process, for one reason or another... and then fail in extreme circumstances.
So, in summary, you are taking a gamble (albeit a small one), and whilst generally you will end up with a device of the same quality, you may sometimes end up with a bit of a lemon.

user41475: If something is too good to be true, it usually is.  
In all seriousness, going with a reputable shop (Adafruit, Sparkfun, Pololu) can save you a bit of headaches later, especially if you are doing integration.  You might ask (email) the Pi Hut folks why you should buy from their place, rather than the other place, I'm curious what they would say.  I don't think this needs to be an accusatory sort of email (how dare you charge more!), but more of a "I see there is a price difference; obviously, something is going on which I don't know about, can you explain this?"
I've bought cheap stuff from Amazon (Arduino clones), and they'd work... after a fashion.  Bad solder masks, badly soldered components; all would make getting things going a real pain. Sometimes, a component (like a voltage regulator) wouldn't work, and so an Arduino clone would work when plugged in to a USB port, but not in a standalone mode.   Then again, this was a 4 for $10, vs 1 for $15, so it was a bit of a lark, but there was a build quality
If you are putting a lot of effort into the software for this, or paying someone for the software to be developed, or this experiment will be a costly one, the price difference wouldn't be as much of an issue.  Is £90 
How many of these are you building, BTW?  If you are building many, cheaper components might be an issue. 
Someone might have another take here; the other shop might be quite reputable, but you have to ask why there is a huge disparity in costs, yes.
If you are wanting to sell stuff online, people may ask for warranties, or expect something to work for N months/years; what would happen if these units fail?

user47766: I designed a battery backup power supply for a product at my work. I included the INA219 current/voltage measurement chip. For the prototype run I bought that part from two Aliexpress sellers since the cost was half of what it would cost through our normal distributors. (two orders of 50) Half of the chips we way out of spec. Some would read current okay but the voltage was off. Some the voltage was okay and the current was off. I suspect one order of the 50 was badly out of spec parts but since we didn't track which chips ended up in which boards we didn't know which was the bad batch. 
In another case, we had been using a cheap buck converter (dc-dc power supply) normally called Mini360. It was a very good module and the chip was from a major IC manufacture. It was cheaper for us to buy the module than to buy the parts so I included it as a through hole component in some of my designs. A couple of months ago we had experienced some problems with a product and I then found that the Mini360 modules we were using was different. The pcb was different, a tiny bit smaller, and the switching regulator use was from a China manufacture. It was a knock-off of the original chip on the earlier Mini360. Because of what we were doing in our product, the new knock-off part caused problems for one of the designs. The part does the same job as the original part, but it wasn't the same. And how it worked for us, in one specific product, meant that I couldn't use it. On the next revision of the product I designed out the module and implemented the module onto our smd board. And we buy the original part from our normal distributors, not China. It costs us more but we need reliability.
For my hobby I use the Arduino framework as it was easier for coding. (I'm a hardware designer) I also use cheap available parts targetted for the Arduino user base. Most of the stuff is decent, good enough. But there always is a higher level of risk when we buy these cheap parts.   

user37523: The cheaper option is not always lower in quality. You can find items for sale on Amazon, Ebay and Aliexpress that all have the same "seller name" and a identical picture of the item. The price is usually 5 to 10 times higher on Amazon than Ebay. Aliexpress is usually the cheapest.
During the past year, I've ordered over 100 Arduino related sensors/modules from Ebay and Aliexpress. Four from Ebay and one from Aliexpress were defective. I got a refund for all five items.
If you are going to buy the cheaper products, it's a good idea to order more than you need in case one is defective.
Some items should not be sold at any price. For example, I purchased a DHT11 temperature and humidity sensor when I first started with Arduinos. It's an inaccurate piece of garbage, and that's exactly where it went. 

48180: <p>My project is an Arduino-based device, packed into a box.</p>

<p>It will need to use Speed, Latitude, Longitude and Altitude data to log hills it detects on to an SD. On the press of a button, it will need to upload the hill data to the server via Wi-Fi.</p>

<p>I need the following items:</p>

<ul>
<li>GPS Module + Antenna</li>
<li>WiFi Module</li>
<li>SD Module</li>
<li>Altimeter</li>
<li>microSD Card</li>
<li>Inline switch for my battery pack</li>
</ul>

<p>The cost? Well on the Pi Hut it was £120 or so:</p>

<blockquote>
  <p>GPS =
  <a href="https://thepihut.com/products/sim808-gps-gprs-gsm-shield-for-arduino" rel="noreferrer">https://thepihut.com/products/sim808-gps-gprs-gsm-shield-for-arduino</a> =
  £42</p>
  
  <p>WiFi =
  <a href="https://thepihut.com/products/wifi-shield-v3-for-arduino-rpsma-802-11b-g-n" rel="noreferrer">https://thepihut.com/products/wifi-shield-v3-for-arduino-rpsma-802-11b-g-n</a>
  = £54</p>
  
  <p>SD = <a href="https://thepihut.com/products/microsd-card-module-for-arduino" rel="noreferrer">https://thepihut.com/products/microsd-card-module-for-arduino</a> =
  £6</p>
  
  <p>microSD Card = <a href="https://thepihut.com/products/blank-micro-sd-cards" rel="noreferrer">https://thepihut.com/products/blank-micro-sd-cards</a>
  (4GB) = £5</p>
  
  <p>Altimeter =
  <a href="https://thepihut.com/products/adafruit-bmp280-i2c-or-spi-barometric-pressure-altitude-sensor" rel="noreferrer">https://thepihut.com/products/adafruit-bmp280-i2c-or-spi-barometric-pressure-altitude-sensor</a>
  = £10</p>
  
  <p>Switch =
  <a href="https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack" rel="noreferrer">https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack</a>
  = £2.50</p>
</blockquote>

<p>On Bang Good (a really cheap online shop I discovered) it was more like £30:</p>

<blockquote>
  <p>GPS = 
  <a href="https://www.banggood.com/GPS-UBLOX-NEO-7N-Satellite-Positioning-Module-For-Arduino-51MCU-STM32-p-1203610.html?rmmds=cart_middle_products&amp;cur_warehouse=CN" rel="noreferrer">https://www.banggood.com/GPS-UBLOX-NEO-7N-Satellite-Positioning-Module-For-Arduino-51MCU-STM32-p-1203610.html?rmmds=cart_middle_products&amp;cur_warehouse=CN</a>
  = £10.54</p>
  
  <p>GPS Antenna = 
  <a href="https://www.banggood.com/GPS-Active-Ceramic-Antenna-IPX-IPEX-Interface-For-GPS-Module-p-1203537.html?rmmds=cart_middle_products&amp;cur_warehouse=CN" rel="noreferrer">https://www.banggood.com/GPS-Active-Ceramic-Antenna-IPX-IPEX-Interface-For-GPS-Module-p-1203537.html?rmmds=cart_middle_products&amp;cur_warehouse=CN</a> 
  = £2.11</p>
  
  <p>WiFi = <a href="https://www.banggood.com/Upgraded-Version-1M-Flash-ESP8266-ESP-01-WIFI-Transceiver-Wireless-Module-p-979509.html?rmmds=cart_middle_products" rel="noreferrer">https://www.banggood.com/Upgraded-Version-1M-Flash-ESP8266-ESP-01-WIFI-Transceiver-Wireless-Module-p-979509.html?rmmds=cart_middle_products</a>
  = £2.53</p>
  
  <p>SD = <a href="https://www.banggood.com/Micro-SD-TF-Card-Memory-Shield-Module-SPI-Mciro-SD-Adapter-For-Arduino-p-919914.html?rmmds=cart_middle_products&amp;cur_warehouse=CN" rel="noreferrer">https://www.banggood.com/Micro-SD-TF-Card-Memory-Shield-Module-SPI-Mciro-SD-Adapter-For-Arduino-p-919914.html?rmmds=cart_middle_products&amp;cur_warehouse=CN</a>
  = £1.02</p>
  
  <p>microSD Card = <a href="https://www.banggood.com/4GB-MicroSD-Card-with-Card-Reader-for-RC-FPV-Camera-Quadcopter-p-1050069.html?rmmds=cart_middle_products&amp;cur_warehouse=CN" rel="noreferrer">https://www.banggood.com/4GB-MicroSD-Card-with-Card-Reader-for-RC-FPV-Camera-Quadcopter-p-1050069.html?rmmds=cart_middle_products&amp;cur_warehouse=CN</a>
  = £3.96</p>
  
  <p>Altimeter = <a href="https://www.banggood.com/MPL3115A2-IIC-I2C-Intelligent-Temperature-Pressure-Altitude-Sensor-V2_0-For-Arduino-p-1198222.html?rmmds=cart_middle_products" rel="noreferrer">https://www.banggood.com/MPL3115A2-IIC-I2C-Intelligent-Temperature-Pressure-Altitude-Sensor-V2_0-For-Arduino-p-1198222.html?rmmds=cart_middle_products</a>
  = £5.16</p>
  
  <p>Switch = <a href="https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack" rel="noreferrer">https://thepihut.com/products/adafruit-in-line-power-switch-for-2-1mm-barrel-jack</a></p>
  
  <p>= £2.50 (From Pi Hut, though)</p>
</blockquote>

<p>I'm suspicious. I might be inexperienced, and this may be a bad question, but is the cheaper option lower in quality? Is the expensive one over the top? The cheap version really seems to good to be true.</p>
 6936: <p>The main reason that some devices on eBay, or where ever, are markedly cheaper is that they are <em>clones</em> produced by a third party, using designs that have been copied/pirated or reverse engineered.</p>

<p>This reduces the third party's set up costs, quality assurance (QA) (i.e. testing) costs and research and development (R&amp;D) costs to almost zero (compared to those of the original manufacturer).</p>

<p>So, <em>generally</em>, the board will, for all intents and purposes, be the same physically, just at a much lower cost, and, as dandavis states in <a href="https://arduino.stackexchange.com/questions/55214/some-arduino-components-seem-ridiculously-cheap#comment116329_55214">his comment</a>, probably with the same reliability and quality. </p>

<p>However, if you purchase these clones, then the research and development aren't being paid for and may inhibit further growth in the market.</p>

<p>In addition, sometimes the cost is reduced <em>even</em> further as the third party cloner will use inferior and cheaper, alternative, components which <em>may</em> cause the device to fail sooner than the original. They may even come from <em>the same factory</em> and be devices that are using the original components, but which have failed the QA process, for one reason or another... and then fail in extreme circumstances.</p>

<p>So, in summary, you are taking a gamble (albeit a small one), and whilst generally you will end up with a device of the same quality, you <em>may</em> sometimes end up with a bit of a lemon.</p>
 41475: <p>If something is too good to be true, it usually is.  </p>

<p>In all seriousness, going with a reputable shop (Adafruit, Sparkfun, Pololu) can save you a bit of headaches later, especially if you are doing integration.  You might ask (email) the Pi Hut folks why you should buy from their place, rather than the other place, I'm curious what they would say.  I don't think this needs to be an accusatory sort of email (how dare you charge more!), but more of a "I see there is a price difference; obviously, something is going on which I don't know about, can you explain this?"</p>

<p>I've bought cheap stuff from Amazon (Arduino clones), and they'd work... after a fashion.  Bad solder masks, badly soldered components; all would make getting things going a real pain. Sometimes, a component (like a voltage regulator) wouldn't work, and so an Arduino clone would work when plugged in to a USB port, but not in a standalone mode.   Then again, this was a 4 for $10, vs 1 for $15, so it was a bit of a lark, but there was a build quality</p>

<p>If you are putting a lot of effort into the software for this, or paying someone for the software to be developed, or this experiment will be a costly one, the price difference wouldn't be as much of an issue.  Is £90 </p>

<p>How many of these are you building, BTW?  If you are building many, cheaper components might be an issue. </p>

<p>Someone might have another take here; the other shop might be quite reputable, but you have to ask why there is a huge disparity in costs, yes.</p>

<p>If you are wanting to sell stuff online, people may ask for warranties, or expect something to work for N months/years; what would happen if these units fail?</p>
 47766: <p>I designed a battery backup power supply for a product at my work. I included the INA219 current/voltage measurement chip. For the prototype run I bought that part from two Aliexpress sellers since the cost was half of what it would cost through our normal distributors. (two orders of 50) Half of the chips we way out of spec. Some would read current okay but the voltage was off. Some the voltage was okay and the current was off. I suspect one order of the 50 was badly out of spec parts but since we didn't track which chips ended up in which boards we didn't know which was the bad batch. </p>

<p>In another case, we had been using a cheap buck converter (dc-dc power supply) normally called Mini360. It was a very good module and the chip was from a major IC manufacture. It was cheaper for us to buy the module than to buy the parts so I included it as a through hole component in some of my designs. A couple of months ago we had experienced some problems with a product and I then found that the Mini360 modules we were using was different. The pcb was different, a tiny bit smaller, and the switching regulator use was from a China manufacture. It was a knock-off of the original chip on the earlier Mini360. Because of what we were doing in our product, the new knock-off part caused problems for one of the designs. The part does the same job as the original part, but it wasn't the same. And how it worked for us, in one specific product, meant that I couldn't use it. On the next revision of the product I designed out the module and implemented the module onto our smd board. And we buy the original part from our normal distributors, not China. It costs us more but we need reliability.</p>

<p>For my hobby I use the Arduino framework as it was easier for coding. (I'm a hardware designer) I also use cheap available parts targetted for the Arduino user base. Most of the stuff is decent, good enough. But there always is a higher level of risk when we buy these cheap parts.   </p>
 37523: <p>The cheaper option is not always lower in quality. You can find items for sale on Amazon, Ebay and Aliexpress that all have the same "seller name" and a identical picture of the item. The price is usually 5 to 10 times higher on Amazon than Ebay. Aliexpress is usually the cheapest.</p>

<p>During the past year, I've ordered over 100 Arduino related sensors/modules from Ebay and Aliexpress. Four from Ebay and one from Aliexpress were defective. I got a refund for all five items.</p>

<p>If you are going to buy the cheaper products, it's a good idea to order more than you need in case one is defective.</p>

<p>Some items should not be sold at any price. For example, I purchased a DHT11 temperature and humidity sensor when I first started with Arduinos. It's an inaccurate piece of garbage, and that's exactly where it went. </p>
