On the 770 front, some of them are selling out on Newegg. Granted, this level of performance was available for about $470 in retail when after-market HD7970GE's launched in July of 2012. In the last 12-18 months a lot of people have already purchased HD7970/670/680s. How many individuals are left to buy a GTX770 12-15 months after GTX680/7970GE came out for $400-450? Whoever is left obviously doesn't follow the GPU market closely or upgrades on refreshes instead of on new nodes immediately. These gamers may be sitting on GTX285/GTX570/HD6970 then but in that case since they upgrade every 2-4 years, it doesn't make sense for them to buy a card with only 2GB of VRAM. That puts GTX770 4GB at $450, which is hardly cheap for what is essentially 1 year old 28nm NV tech or 1.5 year old 28nm gen tech.
780 is probably selling well though since overclocked it can come within 5% of the overclocked Titan for $350 less.
Without actual sales figures, it's difficult to estimate how well these cards are selling. Personally, I wouldn't buy HD7970GE or GTX770 at $400 today. These prices are outrages for what essentially is a performance level of a January 2012 HD7970 @ 1.05-1.1ghz or a March 2012 GTX680 with a mild overclock. Buying 28nm tech for $400 with this level of performance is just as wasteful as spending $400-450 of your money on a GTX580 near the end of its life.
I wonder if for the next series NV will stay conservative and wait another 12 months to launch a 550mm2 Maxwell? If NV releases the large die Maxwell right away, then we'd be looking at 50%+ more performance over the 780 by possibly summer of 2014. That would be spectacular.