OWC ThunderBay 8, the 8-bay Thunderbolt 3 enclosure (dual TB3 ports, 40Gb/s). Fits eight 3.5" or 2.5" SATA drives, works with Mac or PC, SoftRAID-ready. These list ~$900 on eBay.
Mine ran 24/7 hosting eight 18TB enterprise drives that all still test perfect — this thing kept them cool and happy for years. All trays, screws, power cord, and TB3 cable included. Firmware current.
**$700** — cash/Zelle, local pickup, bring a drive and test a bay on the spot if you like.