Marketplace
Unsure of availability but Dick Smith Electronics (Cannington) had the XBOX 360 Guitar Hero 5 bundle (the game and guitar) on special for $98 apparently down from $150 previously and $180 before that.
Cheapest I could find for the bundle was $149. It might go nicely with the XBOX 360 Arcades that people have been picking up. I'm not an XBOX 360 user (yet), this is for my kids, so I can't comment on the game.
I also saw XBOX 360 Guitar Hero Aerosmith for the same price. I'm not sure if this applies to PS3 as well. I can't see it online but there are other's discounted as well.
Big W Liverpool Had Guitar Hero World Tour Guitar Pack for $50 Yesterday on all systems. The whole world tour including drums was $98 they had Aerosmith too i think.