For me, I do not see the need to spend that much on a camera. A used d5 for under half the price works very well for me. I really like the 500/5.6 for the reach and weight, and it works very well on my d5 or d850.
From time to time I think about getting the 400/2.8E + TC or 600/4E, but I have a hard time paying so much for a lens that is so much heavier than Sony/Canon. I'd rather carry around a Canon 600/4 IS III with a 1dxii or r5/6. And the RF lens lineup, for what I would shoot, looks more appealing (70-200, soon 400/2.8, 100-500, etc.). Anyway, I say this as a way of explaining why I don't feel like putting more money into Nikon right now.
Now that Canon has the 100-500 and the R5/6, I might very well head over to to that system.