I think so (not in the US so not sure), usually its off anything in store for exchanges.
NEVER trade games int' Gamestop. They give ya absolutely-**** all for games, then they turn around and overprice said used games for a ridiculous profit. Any other retailer should give you a better price. Better yet, sell 'em another way. To friends, on the internet, whatever; otherwise you're literally throwin' away money. Selling at a retailers should only be done if you're rather lazy (in which case, stop bein' so lazy).
You're not only fostering the issue that is Gamestop, but you're doin' so for less profit. I'd say it's unacceptable, but that's only the case if you're often givin' business to that damned... uh, business.