Locally, my Target's and Toys R Us's are apparently sick of old Guitar Hero games, as they are all being clearanced:
Target:
GH III (guitar bundle) - PS3 or 360 - $24.98
GH Aerosmith (guitar bundle) - PS3 or 360 - $24.98
GH Aerosmith (game only) PS2 - $19.98
GH III (dual guitar bundle) PS2 - $49.98
Toys R US:
GH III (guitar bundle) - PS2 or PS3 - $49.98