They're in business for one reason & one reason only....Pre-Owned games. That's where they make all of they're money. They take in say for examples sake, Deus Ex. They give the consumer no more than $25, not in real currency but credit you can only use in their store. Now that they have your game they'll put it on the shelf pre-owned for $54.99 making a tidy $30 pure profit. On top of the money they get when you use that credit for a pre-owned game. That's why they also steer you towards pre-owned copies because it's all profit to them. Especially when you sell a slightly older game where they can give you $10 in store credit, but sell it in their stores for $44 or higher.
To show you how good this business practice is working for them. Developers are losing more money from pre-owned sales than pirating. That's why game companies are starting to put in those on-line passes if you buy new. If you don't you'll have to pay $10 to use the on-line features. That's due to people buying pre-owned games.
Shop smart, shop at S......not at GameStop.