1. 8800 Ultra is a bad example. It cost $830 at launch and it was only 5-6% faster than the
$599-650 8800GTX. Since then 280/480/580 were all $499 (although 280 launched at $649 but it quickly dropped to $499). GTX285 was
$399 and that was the flagship.
2. Then starting with GK204 (680), mid-range prices at least doubled from $200-249 of GTX460 1GB/560Ti to $500-580 for 680 2-4GB versions. GTX780Ti increased from $499 of 280/480/580 and $399 of 285 to $699. If 6600GT, 7900GT, GTX460, 560Ti sold at $499 and 5950GTX280/480/580 sold at $699 each generation, you would have a point.
3. Even if we go way back, 9800XT was $499, 9800Pro (equivalent to a GTX780 high-end flagship) was $399.
5900Ultra was $499. So your 8800Ultra example is actually an outlier, not the norm. NV has consistently sold flagships at $499-599, 2nd tier flagships at $349-399 (5900XT, GTX275/GTX470/570) and mid-range at $200-250. In fact, the large die GTX275 was
below $300 iirc. That would be the equivalent of selling a GTX780 for $299-349.
4. Inflation is a tricky concept because Intel's prices have barely changed in 10 years but NV increased GPU prices 50-100% in
1 generation starting with Kepler. Secondly, NV shows a spike in gross margins from mid-to-high 30s during Fermi generation, to mid-to-high 40s during Kepler and these have climbed to 53-56% over the last 4 quarters. Therefore, things have definitely changed -- GPUs cost more than ever for the performance level they are targeted at.
The current $550 MSRP for a 980 - a mid-range x04 chip - was reserved for NV's flagships. GTX980 would have been a GTX960/960Ti if we look back at history of NV. I mean the < 15% increase over 780Ti in overall performance already proves that 980 is not a true flagship successor, but it is priced nearly as one.