Motherboard

ASUS Xeon $470

• 16x DDR4 RAM slots (1TB Max)
• 2x Xeon E5-2600 v3 product family (LGA 2011-v3)
• Form Factor: SSI EEB
• 24 pin molex power

RAM

Looks like in general, 4x16GB (64GB) runs around $550, so we're looking at a touch over $2k for 256GB 1 32GB module runs around $500, so for the same price, we could get 128GB, but have 12 free slots instead.

1 64GB module is nearly the same price as the 32: $600. (1TB = 16x64GB of RAM = just shy of $10k)

CPU

These run about $500. Newegg doesn't sell any, but Amazon has them

Other

• Case ~$150
• PSU ~$100
• 1TB SSD $150

Total

$3-4k