I've never understood the outrage over this. Every place that deals in used media does this. Getting a pittance for your used goods has always been the norm for everything, not just video games. It's the cost of dealing with a middle man. They have to resell that used merchandise for a profit, and in Gamestop's case the fact that new video games are a relatively low-margin product means that it makes sense that GameStop isn't paying you $45 for the $60 game you just bought. You want a good return on your used wares? Then take the effort to sell it to the new end-user yourself.
Very well said. With the way some people talk about them, I'd swear GameStop must be putting guns to their heads and forcing them to buy and sell with them.