Found this out of pure luck.
It's $2 per copy + shipping but if you buy 4 or more you get free shipping… but then less people will have the chance to buy it if you care about that at all…
About the game itself, it got an 84 on metacritic: http://www.metacritic.com/game/playstation-3/guitar-hero-wor… and you don't need the guitar controller to play, a standard PS3 controller works just as well.
The next lowest price for this game is $17 per copy off eBay.
You can also get WWE Smackdown Vs Raw 2008 for Xbox360 for $2.50 and Wall-E for the PS2 for $5.00.
ahaha ridiculous price buy 5 lol