For regular backups of 6TB why would you even consider tape? Seriously asking because I have priced tapes and the break even point vs hard drives is high.
Their archival storage tier is extremely cheap, but has a high retrieval cost and a very slow retrieval time. If you wanted to keep 1+ year full and incremental backups of a large amount of data it’d be a no brained. If you’re only keeping 60 day full and incremental than the retrieval cost and time doesn’t pan out cost wise IMO.