First off I don't know this is at all CVS's/Pharmacy so YMMV.
I noticed today in my CVS/Pharmacy Sunday Add, That they had Guitar Hero III: Legends of Rock for the Wii on sale for $39.99. This includes the guitar, also that ad states to while supplies last. You have to have a CVS/Pharmacy card to get it at that price (39.99) if you don't it's $49.99. I say sign up for the card it's free and easy, ask store employee.
These prices is cheaper than GameStop new and used pricing.