gtx 580 is ~ $35 cheaper than the 7950. That seems to be a fair amount, 7950 is slightly faster and it is slightly more expensive.
That is ONE example. I'm hard-pressed to find another recent example of that from either camp, and we all know that at least some of the 40nm issues were TSMC's fault rather than Nvidia's. In fact, the last space-heater we had was 2900xt. At least GTX 480 was slightly faster than its competition at launch, and has gotten better over time. 2900xt was quickly replaced by something much smaller/faster/less power-hungry for a reason; gtx 480, otoh, benefitted enormously from iterative improvements, kept the single gpu performance crown intact for NV for many years, and even ended with a pretty decent reputation for power/heat/noise by the time it was re-spun as gtx 580.
edit: You of all people should know how excellent gtx 480 has ended up. In fact, it's crappy reputation helped us to grab good deals on them after release.
No doubt it has held up well, to the point with the current games on the market I am only after a marginal 20-30% increase in performance over what I have from 3 480s, but want it from 2 cards instead of 3. Pretty decent considering the resolution I play at. I bought into the 480s for the 1.5GB VRAM and SLI scaling was better than it was on the 5XXX series.
What I do see is a new pattern now of nvidia's big die strategy causing them problems in transitioning to new nodes, or perhaps it is attributable to the people who work there that are responsible for making this all happen. First we saw it on 40nm, now we're on 28nm and they're delayed again.
I'm not interested in how it affects them as a company, but for gamers and enthusiasts it's a letdown having to wait on their offerings. On 40nm you didn't hear as much crying over it because AMD was selling their 5870/5850 so cheap relative to the performance and there was a good option. This time round everyone is worked up because AMD is charging a price more in line with what we're used to for halo GPUs and there is this wild hope nvidia is going to undercut them
If the rumour is true that nvidia is first releasing a card with a chip that has a die size similar to Tahiti, I doubt we'll see another space heater, but I'll bet the big chip rumoured to release late this year could be a roaster
AMD has been showing a better ability to handle these new nodes than nvidia did, they did just fine with 40nm whereas nvidia didn't. Now on 28nm again they have parts out and nvidia doesn't, so I'd put the problem in nvidia's hands, not the foundry making the parts. If the first card nvidia releases on 28nm is about the same die size as Tahiti, I think that would give even more foundation to them having trouble with new nodes compared to AMD.