To reserve a copy, you have to pay the amount of $ they ask for pre-ordering, but after the day of release they just sell the stuff to whoever comes first. Pre-orders servers more to let them know an estimate of how much a game will sell. Normally they get an X amount of copies for customers that didn't pre-order and the the other amount depends on the reserved #. If the game gets sold out, they go to the pre-ordered copies and sell those.
If you want to know how bad Gamstop as a company is, just type "Gamestop rant" on Youtube and have fun.
Human Instrumentality Project
Sacrificing older life to create a new lifeform blessed with the fruit of life