Maybe so, but nvidia are clearly making more profit then they have in the past, one look at their share price soaring the past few years tells you that, so not much of an excuse really.What most people don't seem to realize that each new fabrication node is increasing R&D costs by at least a factor of 5 so you can't really compare costs based on die size alone. The 471mm GP102 die costs many time more to produce than the Maxwell GM200 die that was around 600mm^2.
Development costs are exploding
I think Navi might be the time where I spend big on a GPU then sit back 2-3 years enjoying it. As progress may slow down a bit after that and we may not see big gains like we have done in the past.