Once you fill shelves with them. The tape itself is quite cheap (LTO-9 is 18TB for $100), but the drives are expensive ($5000+ for an LTO-9 drive), so you need

Once you fill shelves with them. The tape itself is quite cheap (LTO-9 is 18TB for $100), but the drives are expensive ($5000+ for an LTO-9 drive), so you need quite a bit of volume to make it worth it. You can get an earlier breakeven point by buying used equipment for older generations. But no matter what you do, at small scale hard drives will be cheaper (and can be put on a shelf or in a safe too)