I discovered a nice gem of an insight this week in an article called The 11 Ways That Consumers Are Hopeless at Math: the symbolism of the number 9.

We’re all familiar with the convention of pricing items one penny below a round number: $1.99 instead of $2.00, $39.99 instead of $40.00, etc. Psychologically, marketers know that this works. We’re more likely to buy something at $89.99 than we are at $90.00.

It’s not, though, because we are tricked by that extra penny for our pockets. It’s because, so argues Derek Thompson, the .99 symbolizes “discount.” It is more than just a number, it has a meaning. It now says to us not just 9, but also You are getting a deal. It doesn’t matter if it’s a carton of eggs for $2.99 or a dishwasher for $299.99. In both cases, putting two 9s at the end makes us feel like smart shoppers.

To bring this point home, in those moments when we’re not looking for a deal, the number 9 has the opposite effect. When marketers want to sell a “luxury” item, they generally don’t use the 9s. They simply state the round number price. The whole point of buying a luxury item is to spend a lot of money because you have the money to spend. It shouldn’t feel like a deal; it should feel like an indulgence. Thompson uses the example of lobster at a high-end restaurant. They don’t sell it to you for $99.99. That looks cheap. They ask you for the $100. And, if you’ve got the money and you’re in the mood, it feels good exactly in part because there are no 9s.

Definitely no 9s:

Photo by artjour street art flickr creative commons.

Not yet convinced? Consider as an example this price tag for a flat screen television. Originally priced at $2,300.00, but discounted at $1,999.99. Suddenly on sale and a whole lot of 9s:

Photo by Paul Swansen flickr creative commons; cropped.