If you're gonna buy it off someone at school, you could get it at a much cheaper price than usual.
Tips for haggling:
1) Tell him to bring it to school before you decide on the price. Say you want a good look at the "quality".
2) Appear uninterested. The other guy probably thinks he can get more than he knows its worth, so if he has the price above $30 (GC controllers are about @$50) just tell him "naaah, don't worry about it then, I'll get it a better one of my neighbour/friend/relative" and he'd be tempted to lower the price. He's already brought it to school, he wants to get rid of it, and chances are has already planned what to do with that money.
3) Tell him that his price isn't worth it. If it's next to new, say your previously mentioned intimate has a brand spanking new one which he bought by accident (conjure a random story if he asks why or tell him it's none of his business).
4) Lastly, don't let him call your bluff! If he knows you're lying, then the balance of power will shift.
Get it under $25.