PB PM said:
This argument is still flawed. Why? Because even with the D4 and D800 this still happens today. By your logic, Nikon is still shooting itself in the foot, simply by having more than one FX body.
With all due respect, I did not say Nikon lost sales because of a "FX body." Cameras are more than just a sensor. Nikon lost D3 sales because for all the major features, it was the same camera in a D300 body and $2,000 less. FX is only one very small part and no one just looks at the sensor. It is the all around performance that was basically the same that pushed people away from the D3 to a D700. That is a very different argument.
Besides, you can't lose something twice without gaining it back. D3 sales were lost. Some were regained by the D3s, and even more by the D4 as the D800 does not do that segment (sports/press/extreme low light) well and people bit the bullet and moved up. The niche that Nikon created have now been occupied by studio/landscape/low action shooting and has pulled some customers from Canon and probably a small few from medium format land.
D3 -> D700 = Apples to apples (with a small bite out of it.)
D4 -> D800 = Apples to grapefruit.
Unlike the D700, the D800 is a very, very different camera than the D4. Most shooters who need a D4 can not replace one with a D800. If you need a back-up D4, the D800 will not get you there. D3 could get 9 FPS, D700 with grip 8 FPS. The D800 can not do that. If you look up historical sales from amazon you can see the D3 sales plummet when the D700 hit the market, and they never recovered. Many pros kept it even when the D3s came out as the improvement was not that much, and the gains were not worth the cost.
Now what many D4 owners love is that those who bounce from sport to studio work and who wanted a High resolution camera for a second system, only had the choice of the $8,000 D3x. That did not sell well at all. The D800, and even the D600 to a large degree, have ate that camera's market up for $5-6k less. But again that is a entirely different use than what the D4 is intended for. At the D800 launch Nikon addressed this over and over again how unlike the D3/D700 where they were essentially the same camera, The D4/D800 are two entirely different systems. Basically they have taken Canon's model that they use for their 1Ds/5D line - one for press and sport, and one focused on studio and landscape.
The high iso performance I mentioned above. I don't think the D4 gets enough credit. There is more to measure than just "off color specs" for high iso comparison - The D4's Color depth (i.e. not washed out) is unbelievable. It is much better than my D800 at stratospheric Isos for sure.
If you can recall back to 2008, Nikon was quickly trying to make an answer to the outdated Canon 5D and needed something to combat the release of the 5D MkII. They obviously had nothing in the works, so they did in essence what donaldejose said above - they just dumped a D3 sensor into a D300 body and changed the viewfinder. Their frankenstadion camera turned into one of the most sought after cameras.