Nikon D4s

It seems like the Nikon DSLR prices are on a downward trajectory.  An used D4s with shutter count less than 36,000 is asking for $2,200 and having a best offer price option.  I can see the price can be talked down to very close to $2000 if there is no bid.  The frenzy goes to I guess the Z cameras or the D850.  I have never touched a D850 and I don't know how great its AF is.  For me it's all about the AF.  The D single digit line series just gives me more confidence in that regard.  Of course I could be wrong.  Based on my D810 experience the AF is good but I wish it could be better.  Again, the myriad of variables and user technique can render my opinion less than objective.  Anyway, I think the D4s comes down to $2000 is really something.  If the D850 set, meaning the camera and battery grip, sells for less than $2000 and if the AF is really really as good as the D5 then sure why not.