One of the things Sharma confirmed is that the R600 is made on a 80nm process:
In an interview with Sharma, the site asks how big an advantage using 80nm process technology instead of 90nm presents for the R600. Sharma replies:
Yeah, I think the big advantage that 80 gives you over 90 from a process perspective is transistor density. You just get more and the chip will cost less for a given transistor count than it would at 90.
Later, he adds:
So the choice of 80 was aligned with what we need to deliver and it did give us a cost advantage over 90. So we choose to go that way.