>> How many would pay $2500 or more for a camera that did most of what was desired?
The D90 retailed for $1000. The D7200, two evolutions later, sells for only $300 more but incorporates much of the D300 feature set missing from the D90.
I don't see any real evidence or even a good speculative basis for the idea that a D400 would cost any more than a D300 as long as no additional features were added except the total bandwidth needed to move 24mpx x 6-8 fps. And the way electronics evolves, that bandwidth, when available, is not necessarily much more costly.
And in the meantime, the incorporation of many of the upscale features, such as 51 pt AF, into a higher volume body like the D7200 increases economies of scale that just as likely make a D400 even cheaper to produce.
They could even use the same identical (D300) metal body fabrication, saving even more money. I doubt if any D300 users would complain about not having to relearn yet another round of button changes. And most users believe that body was about perfect. That is why so many are clamoring for an encore.
The D300 sensor was a very new sensor, in terms of a large scale production "cheap" 12mpx sensor. They would likely use basically the same sensor already used in the 3 lower tier bodies, the design and fabrication of which is basically completely amortized by now. If it's basically the same sensor in the D3200, it must be relatively dirt cheap. That should be a huge cost advantage.
In other model lines, prices have been relatively stable, and even trending down when considering the increased feature packages.
We can only speculate on costs but what exactly is the basis for suggesting that a D400 would have to cost $2500 or anywhere near it? How much blood Nikon wants to extract from its customers (in the form of margins) is another story entirely.