Normally it’s a walk of shame for gamers to lug a pile of games to GameStop to get pennies on the dollar in cash or trade-in credit for stuff they probably didn’t finish and overpaid for. But a deal going on right now for the proverbial “limited time only” offers 50 percent in bonus trade-in credit for your games.

Joystiq did some research and discovered the following games will net you $35 in trade-in credit: Modern Warfare 2, New Super Mario Bros. Wii, Dante’s Inferno, and BioShock 2.

But the zinger comes with Mass Effect 2, which will net you $52 in trade-in credit, and $57 if you’ve got a GameStop edge card. That’s only $3 less than the game costs new. So in theory you could buy a used copy of the game for $55 — or about $50 if you have an edge card, and trade it back in on the spot for a $7 trade-in credit profit.

GameStop offering 50% bonus on every trade-in [Joystiq]

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