How much does Gamestop buy used Xbox 360 games for?

My Xbox just got the red ring of death and all my friends have PS3. I therefore intend to sell all of my games and buy a PS3. I have 34 Xbox 360 games and two original Xbox games. Some games are very new, but others are quite old.

I sold a few Xbox games not long ago and they gave me 2-5 dollars each. rip off. Xbox 360 is expected to be about 10 for very old and about 20 new ones.