Upload & Sell: On
As I stated in my original post, I never intended on buying the D600 just to return it.
I've been really surprised at all of the flack you took on that.
The dealer makes out either way. Hopefully in long term good will, through providing good customer service. And word of mouth sales.
But also immediately in profit. This is how I would figure it if I were him:
I sold a Nikon D600, so I made 2 units of profit at $2,000 - one for each $1,000, call that 2P.
Now, the customer is looking at a D800. If he buys that at $3,000, I make 3 units, 3P. So I make some additional profit. 3P-2P = +1P
Even if I get the D600 back, I can almost certainly sell it as a "demo" or "used" at my cost. If I am lucky, I can actually make an additional 1 unit of profit.
So he starts out having made 2P. By "upselling" the customer on the D800, he at minimum makes an additional 1P of profit (with no additional net profit on the D600.)
Or, more likely, he makes the additional 1P on the D800, and 1P on the D600 resale, for an additional 2P profit. Plus all of the customer good will, future word of mouth, etc.
If the D800 were in high demand so that he couldn't replace the body he just sold he might be more reluctant. But when he can replace it immediately from Nikon stock, this is really an opportunity for him (especially with the D600 being the newer and likely more in demand body right now.)
I say this as someone with an MBA and 20+ years experience in business, both my own and others. That is the way I would look at it. The current situation is called a "sunk cost" - you can't change the past. The question is what happens going forward.