I would estimate the cost for three years like this:

- 1U single socket Supermicro Xeon E5v4-2630 10core+1GTX1070 GPU = 1500EUR

- operation costs (power+cooling) over 3 years = 1500EUR

- cost of 2 hardware admins 160k/year

- renting local rack space 15EUR/U

This equals about 145 servers for 3 years for us for 1 Million. The setup is highly optimized for _one_ set of data crunching tasks, not DB. We do not need much ram, or network but require a specific CPU/GPU ratio.