So I did it, I purchased a used Nikon D850. I did get a good deal, but why did I buy it. Functionally it is very similar to my Nikon D500. In fact there are a few areas where the D500 is superior, faster burst speed, lighter, better focusing, etc. but the one area the D850 wins is resolution (as well as theoretical image quality, but I will have to test that)
Now if I would just post images on this website, instagram, or the internet in general, or if I did not print too large, resolution would not be important, however I have started printing larger, and submitting to sites to produce merchandise (redbubble.com). I also have another project where resolution may become more important.
I did look at the mirrorless Z7II which is, in many ways, the successor to the D850, however I did not like the viewfinder. My eyesight is well above average (I recently had it tested) and I could not get used to the low resolution, not to mention the minor lag, in the viewfinder. If I used the rear display more than about 50% of the time, I guess I could live with it, but I still like an optical viewfinder.
As it happened, I offered a lowball price on the D850 and ended up having to buy it. Other than a short walk to test it out, I have not shot with it. Hopefully I can get some images up soon.
UPDATE-May 30: I went to Butchart Gardens to try out the camera, but I got hung up testing the focus stacking feature and did not get any images I want to publish at this time. There are a few quirks to the camera, but so far I like the way it handles.