I just browsed eBay a bit and saw that older, used SAS drives can be had pretty cheap - 30€ for 4TB, but of course rather old drives, sometimes 10 years old.
Now, I wouldn't expect ultra reliable, ultra fast, super cheap drives here. But this offer seems compelling, even buying a spare drive for higher redundancy would still be pretty cheap.
Question is: am I too optimistic here? Are these drives bound to fail within 3 months?
I'm running 4 Seagate exos 10tba sas3 drives. They're fast, quiet, and don't use a ton of power.
Now you can get 14 and 16tb drives now for the same price.
Honestly, at this point, I'd rather sell the SAS drives and go back to SATA. I don't need an insane amount of storage, and the controller adds power usage.