I recently had a similar experience, although not this size.
Pre-story:
For 3 years I wanted to build a rack-gaming-server, so I can play with my son in our small apartment where we don't have enough space for a gaming computer (wife also doesn't allow it). I have a stable IPsec connection to my parents house, where I have a powerfull PV plant (90kWp) and a rack server, for my freelance job.
Fast forward to 2 months ago, I see a Supermicro SYS-7049GP-TRT for 1400€ on Ebay. It looks clean, sold by some IT reuse-warehouse. No desription, just 3 photos and the case label. I ask the seller whether he knows whats in it and he says he didn't check. The case alone comes new at 3k here in Germany. I buy it.
It arrives. 64GB ECC memory, 2x Xeon silver, 1x 500GB SSD, 5x GBit LAN Cards. Dual 2200 Watt PowerSupply. I remove the airshroud, and: A Nvidia V100S 32GB emerges. I sell the card on ebay for 1600€ and buy 2x Xeon 6254 CPUs (100€ each) to replace the 2x Silver ones that are in it. Last week, I bought two Blackwell RTX 4000 Pro for 1100€ each. Enough for gaming with my son! (and I can do some fun with LLMs and home assistant/smart home..)
The case fits 4x dual-size GPUs, so I could fit 4x RTX 6000 in it (384GB VRAM). At a price of 3k, this would come at 12k (still too much for me.. but let's check back in a couple of years..).
Buying used enterprise gear is fun. I had so many good experiences and this stuff is just rock solid.