Yeah, it is about $100 more expensive than the PC version, but on the other hand it offers the dual-link DVI ports, when most Windows-compatible 6800GTs and even Ultras come with the standard DVI + VGA port configuration.
In fact, NewEgg only has one dual-DVI 6800GT in stock right now, and it's $450. And that's for standard DVI, not dual-link. I don't know how much it is to get a dual-link card on the PC side, but I think $500 is about the minimum.