This obviously won't last for very long, but Amazon is technically paying their own customers to buy Playstation All-Stars: Battle Royale from them. How exactly did this happen? Well its all thanks to Sony's cross buy promotion and a poorly timed sale. Here are the details.
As you all know, every brand new copy of Playstation All-Stars comes with a free Vita version of the game. The PS3 version of the game itself is currently on sale at Amazon for $30. While that would normally just be an okay deal, you have to factor in their current promotion where if you trade $20 worth of games into Amazon, you get an extra $20. How much does Playstation All-Stars trade in for? $22.
So if you were to act now, you could buy Playstation All-Stars for $30, trade it in for $40, and then keep the Vita version of the game for yourself. You're essentially getting paid ten dollars to own the Vita version of the game. But again, this is only going to go on for so long before Amazon realizes that stacking sales and promotions like this is a bad idea. So if you're going to stick it to Amazon, you better do it quick. You can view the sale page below.
EDIT: Surprise surprise. Amazon has cut the trade in value in half. So no more free games and money for you.