Do you know the cost of manufacturing an FX sensor compare to a DX sensor?
Anyway, the price is not just an objective value. It is also a subjective one. I really wanted the D3 because of the FX format and its high ISO performance. Plus the fact that now my lenses would be working at their true focal length. The joy of using my 85/1.4 like a 85 mm lens again! I didn't try and calculate if it was really worth that much more money than my D2X. That's the camera I wanted. Period. I also wanted the two new Nikon zooms, 14-24 and 24-70. To afford all that, I had to trade in all the camera equipment I had, including the D2X and a Hasselblad V system. Then, of course, the D3 was very big and heavy - especially with the 24-70 on - to go out with. So I traded in my D200 for the D300, which has many superior features, but I'm missing the high ISO performance when I go out. Now, they'r offering me the best of both world! Full frame AND small and light. Exactly what I want (Need? No. Want, yes.) So, if I can trade in my D300 for the D700 and some extra cash, I will do it. For me it's worth it. I will not make better pictures (well, I may at high ISO) but I'll be happier doing it. Is it worth double the price of the D300? Objectively, I don't know. Subjectively, yes. YMMMV