It makes sense. I'm almost certain that a Fiji GPU costs more than a GM200 GPU to manufacture for a few reasons:
- While the Fiji die is <1% smaller, it has >10% more transistors, meaning it's likely more complicated to produce
- HBM is significantly more expensive than GDDR5 - it's completely new tech, vs GDDR5 with its roots in DDR3
- The silicon interposer to allow 2.5D "stacked" VRAM is a separate die entirely, built on a 65nm process; GM200 does not need this die for obvious reasons
Granted, the interposer has no logic and is more or less a fancy circuit board. That said, Fiji is almost certainly one of the most expensive GPUs to be manufactured in recent years. AMD knows this, if Nvidia doesn't yet they will once Pascal nears launch, and it simply isn't feasible to slap HBM on everything.