I'v been searching to find a good price for this game as well, since I sold my xbox 360. The best price I have seen so far is Ebay where you can get a new one for around 40-45$.
My local Gamestop had a used PS3 copy for $35 a couple weeks ago but I didnt see it last time I was there. Your best bet would probably be ebay at this point.
Nice avatar btw. I still bump the two CLASSIC HBMS albums on the regular! Time for a 3rd joint!