Or BD-Rs. 50GB on a single dual layer disc. Haven't finished the last spindle I bought, but I assume they're the cheapest per GB by now.
Checking diskprices.com - https://diskprices.com/?locale=us&condition=new,used&disk_ty... - there's a cheaper outlier for DVD-R, then it's 25GB BD-Rs for a bit.
LTO tape can be cheaper, but the cost of the drives has long been an obstacle to dabbling.
Yeah, the prices don't seem to be correct. New 16TB HDD for $200. DVD+R 25x pack for $2, etc. Clicking the links shows different prices on amazon, etc.