About $8000 plus the GPU. Let's throw in a 4080 for about $1k, and you have the full setup for the price of 3 RTX5090. Or cheaper than a single A100. That's not a bad deal.

For the hobby version you would presumably buy a used server and a used GPU. DDR4 ECC Ram can be had for a little over $1/GB, so you could probably build the whole thing for around $2k