That is a fucking great deal, especially since I do not like this game at all. Hello 3DS and fire emblem.
I'd really love to know how many people are strolling into a GameStop, asking for this low-print-run, year-and-a-half old JRPG that they somehow expect GameStop to still have copies of. Or maybe GameStop has some other data avenue that led them to realize "Oh shit, we should get copies of this game in stock, even if it means giving $48 trade-in value". OK, I guess it must be other data avenues that told them to do this, but I still don't get it - even if they get a couple used copies in stock, the kind of JRPG afficionado who knows they want this game probably isn't going to think about getting it from a GameStop.
Anyway, it's usually a bad idea to trade stuff in to GameStop, and the only excuse I could see for using it is if you're a minor and your parents absolutely forbid you from using eBay to sell things.