> Of course, tapes require a tape drive and its cost would require a lot of data to compensate the cost, but at a such high cost of retrieval it would not take much data to equal the cost of a tape drive.

But the less you expect to use it, the less this matters.

So I'd put the break-even point a bit higher. Tape is good for 100TB or more but for tens it's hard to justify a tape drive.

Also it's important to remember to get those tapes offsite every week!