That price is unlikely. If it had been an f/8 lens, then that price would make sense as an extrapolation of the prices for the 300/4 and 500/5.6. At f/6.3, though, it's going to have to be considerably more expensive.
Egg on my face, again. The US price is $6,496.95. That's amazing. Maybe Nikon has developed new and cheaper manufacturing techniques for the PF element.
I'll make yet another risky prediction. Because the price is so low, this lens will be very hard to get for a long time. I can see the Z9 and the 800PF combination being in tremendous demand for wildlife photography, especially for those shooting smaller birds.
Personally, I'm very happy with my 500 PF, the capabilities of which I've just started to explore, so I won't be getting into the very long line for this new lens.