@sfitzjava:
The reason they are more expensive is because they need a special video bios that can cope with the PPC. Since they sell in such low numbers the price is higher to cover the development and manufacturing costs.
SmartFirmware has some sort of x86-emulation layer which makes it possible to use standard x86 graphics cards. I don't know the details of it. So far it seems you lose of-video (afaik it's Apple's version of VESA). It's not much of a loss though as framebuffer drivers generally work much better (and it's not even an issue if you use MorphOS).