Here is what I'm looking at:
R9 270x vs. GTX760: GTX760 is 20-25% more expensive but only has ~8-10% faster performance, so R9 270x wins in value.
R9280x vs GTX770: About the same price now and GTX770 is ~8-10% faster, so GTX770 still wins in value.
R9 290x vs GTX 780ti: 780ti is 27% more expensive but only has ~10% faster performance, arguably about even at higher resolutions. So R9 290x wins in value.
IMO the 760 is definitely no longer a "mid-range value leader" now that AMD pricing has come back down to Earth. For the high-end cards, you have all 4 cards listed. IMO, the R9 290X is clearly the best GPU for the $$, within striking distance of the 780ti for significantly less $$.
R9 270x vs. GTX760: GTX760 is 20-25% more expensive but only has ~8-10% faster performance, so R9 270x wins in value.
R9280x vs GTX770: About the same price now and GTX770 is ~8-10% faster, so GTX770 still wins in value.
R9 290x vs GTX 780ti: 780ti is 27% more expensive but only has ~10% faster performance, arguably about even at higher resolutions. So R9 290x wins in value.
IMO the 760 is definitely no longer a "mid-range value leader" now that AMD pricing has come back down to Earth. For the high-end cards, you have all 4 cards listed. IMO, the R9 290X is clearly the best GPU for the $$, within striking distance of the 780ti for significantly less $$.