Speculation as to why Thom or I (and I can actually only speak for myself) buy and sell the equipment that we do is uncalled for and totally speculative. My situation is unlike that of anyone else. Though I accept short term loans of gear from major manufacturers for testing (especially pre and early production models), these are always returned within days, rarely held for longer than a week or at most two.
Because I believe in long term and field testing (and that's one of the things that makes my reports different that those of other reviewers) I buy the cameras and lenses that I use. Then, every year or two I sell them to free up capital for new purchases.
It means that I can test and use a wide range of equipment over extended periods. When something especially appeals to me I hang onto it it for a long time. I have several cameras that are in that category. Others come in and out in just months, or a year at most, being replaced by the latest model for use and testing. This is my business model. This is why a million people a month visit this site, to read my reports and reviews. It works for me.
But, even if buying cameras wasn't a business expense, as it is for me and many pros, and even if one can afford something, that doesn't mean that it's good value. May late fatherinlaw was a wealthy man. But, he'd drive two miles out of his way to buy gas for 2 cents a gallon less than at the station across the street. When I asked why, his reply was simply that it was the principle of it.
That's something of what I feel about the D3x and why I cancelled my order. Yes, I can afford it, but I simply find it to represent poor value. After testing the 24MP Sony A900 (which I purchased for less than the equivalent of US $2,500 here in Toronto last month) the thought of paying US $8,000 for a camera that that has the same resolution, the same frame rates, etc, etc, just seemed to me to be a bad value. The Canon 5DII is also well under $3,000 as another alternative in a full-frame 20+ MP camera.
With the value represented by the Nikon D700 as compared to the D3, and Canon 5DII as compared to the 1Ds MKIII, I feel that the days of the mega-pro DSLR are numbered. As Bernard wrote above, Nikon has just come late to the game, but the game is changing.
Cameras like the Leica S2 and forthcoming Nikon MX are, in my view, going to take their place for many photographers seeking a new high end. Yes, there will be some that buy the D3x, just as there are still those that buy the wonderful Nikon F5 film camera. Nikon is known for fighting rear-guard actions and doing so well.
So, I'm sure that Nikon will still sell some D3's and D3x's, and Canon some 1DMKIII's and 1DsMKIIIs, but I now believe that the days of these cameras as mainstream are passing, as much lower cost and competent alternatives become available.
That was the reasoning behind my cancellation of my D3x – simply the acceptance that an era has passed and that value wasn't there (for me) at that price point. It might be for others though.