If you're crafty you can work around this- three of my servers (2 NAS boxes and a Proxmox box) were custom built from commodity hardware. I literally bought plain ol uATX and ITX decommed business gear from my local uni surplus store and a P-Link chassis for each used from eBay. I spent more on drives than I did machines (Y'ALL WANNA KNOW HOW MUCH IT COSTS TO BUY 16TB WORTH OF SSDS FOR ZFS MIRRORS? TOO. DAMN. MUCH.)

You really gotta do some due diligence to make sure you're not buying lemon parts but it's very possible to get a beefy homelab at fair prices!