Hard to get recent PS3 games that cheap. BTW Mafia 2 on PS3 had very bad graphics and had frame rate issues, why would you want to play that game on PS3?
They surpassed every online store with quality service, FAST shipping, and low prices.
Also see cduniverse.com
If you don't have a store like Gamestop or a record store like Dimple that will take trade-ins, you can send used games to Amazon.com for store credit... that is, if you have games you want to trade in...