Yes I guess for 80TB and 5 years, LTO starts looking better. For 20TB, StorageBox is still ahead.

Per https://aws.amazon.com/s3/glacier/pricing/ it looks like Glacier costs $3.6 per TB per month, which is a lot more than StorageBox even not counting egress fees. Is there a cheaper class of Glacier that I missed?

Another idea is simply to buy a 29TB hard drive or pair of them to keep spinning, doing occasional integrity checks. I've had terrible luck using HDD's for cold storage but by now have had a few spinning in servers for 5 years without failures. Those are hosted servers in data centers though. Environmental conditions at home might not be as good. Two HDD's idling might use $100 of electricity over 5 years.

An LTO7 drive on ebay is $1000+, while new is still close to $4000. I'm dubious of used tape drives but maybe it is an ok idea. Hmm. New LTO7 tapes are around $50 (6TB capacity) so just barely ahead of HDD.

I wonder why there is no "LTO as a service" where someone has an LTO drive in a data center, and for a fee will write a tape for you and ship it to you.