Ebay isn't too bad of option either, I got a new/sealed copy for $44.96, but I'd been watching a while before the right buy it now deal came around.
The game is a blast btw, I have my GH3 guitar ready to go. I had originally bought the entire rock band set up from Costco, but my guitar developed the strum issue so I returned the entire thing. I really missed the game though. It is awesome how the crowd sings along with the song when you are really rocking. Having played GH3 the big thing missing for me was the crowd really getting into the song when it is compared to Rock Band.