Higher prices for the rest of us. Costco used to have a generous return policy too but people abused it. People casually buying each with the intention of returning one... people buying 2-3 so that they can pick the one with the best screen, etc..... all of those returned iPads don't disappear, they end up having to get shipped back, refurbished and listed for sale at a lower price, which results in a much higher cost for Apple which they must pass on to consumers.
Fortunately OCD freaks make up a relatively small segment of the overall population.
No. Apple wants you to be happy with your purchase. They don't want you to be stuck with a device you don't like. Your reasoning may apply to other vendors, but Apple's pricing structure is built differently, and their profit margins allow for this. And, like you say, this is not something most people do anyway.
They get you with your iTunes purchases on the back end, so don't worry about Apple profits. They are doing just fine.