I know for a fact that the last couple months ati has started to use different sized roms in mac and pc versions of cards. this will prevent flashing and that obviously was the goal of ati. the reason they charge so much more for mac versions is because mac cards only amount to about 10% of their product sales (including oem). they have to put extra work into something that makes less $ so therefore it costs more.
_________________________
Mac mini C2D 1.83GHz - 2GB RAM - 200GB 7200rpm HD
Sawtooth w/G4 1GHz - 1GB RAM - SIIG SATA w/2x1TB HD
B&W w/G4 600MHz - 1GB RAM - 2x80GB HD
Sawtooth G4 400MHz - 512MB RAM - 40GB HD
Dell Ultrasharp 2007WFP 20" Widescreen LCD
2.94TB Total Storage