hedwards: It's got nothing to do with psychology.
I think it does.
I'm sure that after some thinking, people will infer the correct price, but I think they count on that small time frame it takes for you to process things to make an impact.
There is a common saying: "You never get a second chance to make a good first impression".
Take an hypothetical scenario:
You are shopping around in a store (or on a digital web page, doesn't matter).
Then, you pass on some product that is priced at 10$, but you have it firmly set in your mind that 10$ is too pricy for such a product so you'll pass it without giving it a second thought.
Now, let's say it's 9.99$. For at least a split second, you'll look at the most significant digit (yes, people don't analyze the entire price as a whole, they break it down into the sum of it's parts... I do it all the time when I do arithmetic... it's one of the oldest arithmetic trick in the book) and deduce that it is less than 10$.
For that split second, they will actually take a look at the product and consider the product because it got past the "price gate" in the brain.
Yes, the person will then look at the cents, see 99 cents, round it up to 1 dollar and add the dollar to the most significant digit, making it 10.
But it's too late, the product already got past the price gate and is now in the person's head.
From there, it really depends on how attractive the marketing gurus made whatever is on the box.
Does it have cool colors? Cool shapes? A cool title? Does it highlight well the special features the product has that other similar products don't have? Etc.
You need to consider how the human brain actually works, rather than consider it like a perfect disembodied machine tied to some perfect universal logic.