use case. total storage capacity, chassis size & cabling constraints, physical drive size, and power.
I looked at a bunch of different drives (and prices) when designing out
my 100TiB mITX build. I stared hard at the 8TB QVO (QLC). I ultimately went down the path of sourcing used "8TB CLASS" (7.68TB) enterprise capacity tier TLC SSDs. These can be found in quantity < 600 each if you are patient and willing to research and then communicate with sellers on the bay. The TLC tend to have a bit of a better performance curve than the QLC.
Ideally 12 or so SAS 15.36TB would have been about perfect - my chassis would limit me to 12 drives, and a wide vdev rz2 pool would have been great or a 2 x 6 RZ1. Problem is I could not find any (in the used market) for < ~1500USD per drive in quantity.
For my use case, < 20 vms/dockers and media storage, I wanted a mix of reasonably performant drives (vm's) and capacity. I ended up using a hybrid: pair of 3.84TB nvme for my vm's and 18 x 7.68TB enterprise TLC Sata SSD's (Micron 5100 ECO And Micro 5200 Pro) in 3 x 6 RZ1
30TB SAS SSD's aren't really showing up in the used markets. Heck 15TB SAS SSD's aren't really showing up in large quantity in the used market, IIRC there's one seller with a decent quantity - but (as of my last communication) they won't go < 1450 / drive.
