user7889: I am starting with Arduinos, coming from the world of Linux (with the RPi as a bridge) and after having tested some setups I now wonder where to go next in implementation.
What I am trying to understand is whether it is recommended (time and cost-wise) 

to create a standalone, circuit-board based version of whatever I prototyped on the breadboard, with a micro-controller with connections trimmed down to what is needed for that specific setup?
or rather just look at neatly packaging the Arduiono with the breadboard and wires in a case?

I expect to build 5 or 6 of the same simple setups (to put in various places in my house).
Note: there is a similar question (with almost the same title) but it deals with the legal aspects of commercializing a setup.

user368: 
with the breadboard

That phrase right there makes the solution a non-starter. Solderless breadboards are good for prototyping, but are too fragile for use in a final project.
As for whether or not you should use an actual Arduino or reduce the circuit to a minimum, that is between you and your wallet. It is possible to make a basic AVR board (including MCU) for under $6 in parts, but the time investment is not entirely trivial.

user6740: I started using an Arduino (Uno), and a solderless breadboard, to do my prototyping. 
After the 2nd project, I started programming the Arduino, then pulling the AtMega chip off the board (if you have a through-hole chip rather than a surface mount one) and plugging that into my breadboard (you will need some supporting circuitry for this - a clock and a powersupply e.g. batteries). The AtMega has a larger range of voltages than the Arduino, and can be run up to 20mhz. You will need to jiggle some constants for this, or be ready for your delays to run quicker too.
I have since bought an USBISP (see Google), which can be hooked up to the Arduino board (there is a 6 pin header made for this, on the opposite side to the USB), or can be hooked up to specific pins. With this, I have started programming AtTiny chips - smaller, easier to set up, fewer pins to interface with, and really, really cheap!
All my long-term projects are on veroboard (see Google) - solder everything on, then cut it to the size you need. It's worth spending time before you solder working out your layout.
If you want to produce these in bulk, I would suggest getting some prototypes on veroboard first (you will, invariably, make changes once you start testing!), then when you're happy, you can copy the veroboard design (possibly tweaking it to optimize for greater flexibility), and order PCBs from a company that does this sort of thing. 
Good luck!

7889: <p>I am starting with Arduinos, coming from the world of Linux (with the RPi as a bridge) and after having tested some setups I now wonder where to go next in implementation.</p>

<p>What I am trying to understand is whether it is recommended (time and cost-wise) </p>

<ul>
<li>to create a standalone, circuit-board based version of whatever I prototyped on the breadboard, with a micro-controller with connections trimmed down to what is needed for that specific setup?</li>
<li>or rather just look at neatly packaging the Arduiono with the breadboard and wires in a case?</li>
</ul>

<p>I expect to build 5 or 6 of the same simple setups (to put in various places in my house).</p>

<p>Note: there is a <a href="https://electronics.stackexchange.com/questions/64280/what-make-now-that-i-have-implemented-a-working-prototype-of-my-system">similar question</a> (with almost the same title) but it deals with the legal aspects of commercializing a setup.</p>
 368: <blockquote>
  <p>with the breadboard</p>
</blockquote>

<p>That phrase right there makes the solution a non-starter. Solderless breadboards are good for prototyping, but are too fragile for use in a final project.</p>

<p>As for whether or not you should use an actual Arduino or reduce the circuit to a minimum, that is between you and your wallet. It is possible to make a basic AVR board (including MCU) for under $6 in parts, but the time investment is not entirely trivial.</p>
 6740: <p>I started using an Arduino (Uno), and a solderless breadboard, to do my prototyping. </p>

<p>After the 2nd project, I started programming the Arduino, then pulling the AtMega chip off the board (if you have a through-hole chip rather than a surface mount one) and plugging that into my breadboard (you will need some supporting circuitry for this - a clock and a powersupply e.g. batteries). The AtMega has a larger range of voltages than the Arduino, and can be run up to 20mhz. You will need to jiggle some constants for this, or be ready for your delays to run quicker too.</p>

<p>I have since bought an USBISP (see Google), which can be hooked up to the Arduino board (there is a 6 pin header made for this, on the opposite side to the USB), or can be hooked up to specific pins. With this, I have started programming AtTiny chips - smaller, easier to set up, fewer pins to interface with, and really, really cheap!</p>

<p>All my long-term projects are on veroboard (see Google) - solder everything on, then cut it to the size you need. It's worth spending time before you solder working out your layout.</p>

<p>If you want to produce these in bulk, I would suggest getting some prototypes on veroboard first (you will, invariably, make changes once you start testing!), then when you're happy, you can copy the veroboard design (possibly tweaking it to optimize for greater flexibility), and order PCBs from a company that does this sort of thing. </p>

<p>Good luck!</p>
