I feel that 1.900 for a used D810 is not the best price you can find. A quick search through "sold items" on US
eBay shows that 1600 seems to be a good price if you are ready to wait a while.
But: For half the price you can get a D600 which is nearly as good and you still have a lot of money left for lenses, new and used.
The trinity is nice but zooming is not for everyone and every situation. The 14-24 is very good but I did only use it as a 2.8/14, which does not exist in comparable quality as a prime. The optical quality of the pro zooms is phantastic and the AF speed generally better than most of the Nikkor primes.
It is thus not the optical Quality that made me buy prime lenses although they were more expensive. It is the fact that I am used to work with two bodies and two primes and my field of work is not in sports and action.