It just seems like the right time to pull the trigger, in spite of using credit (interest-free, if paid within a year). It seems to me that the Z8 is getting some people with low usage D850 cameras to trade those in for the latest, greatest thing. I suspect later that the D850 copies that come on the market will have more shutter actuations and therefore be less of a bargain.
As a value proposition, this will by far be the best deal I've had on a camera. Adjusted for inflation and factoring in expected usage, I paid way more for a new D70, which was my first DSLR. I also paid more for two new D200 cameras (bought separately about a year apart), a new D300, a used D800 (which had more actuations than the D850 is supposed to have), and for a lightly used D500.
I plan on keeping my D800 as an emergency back-up, using my D500 as a day-to-day camera, and using the D850 for nature/landscape and special occasion photography. I also anticipate situations where I have both the D500 and D850 at the ready with wider angle lenses on the D850 and more telephoto lenses on the D500.
I will update this thread when I have the D850 in-hand and start getting it ready for use. I will be testing the D850 against my existing cameras with various lenses I have, set-up UniWB and customized Picture Controls, etcetera.