Many years ago, when LTO-7 was new and state-of-the-art, I have bought a new tabletop tape drive (Quantum) for $3000, which is less than an Apple HMD, but much more useful for me.

After writing several hundred TB, I have achieved a decent money saving in comparison with using HDDs.

On the other hand, when someone needs to store only 100 TB or less, there is no chance to recover the cost of the tape drive, so tapes are inappropriate for such a case.

    After writing several hundred TB

Sheesh, what are you writing!?

With scanned books and Blu-ray movies, the TBs add very quickly when you do not want to degrade their quality with additional compression, which is my case, because after digitizing or ripping them I do not keep the originals, due to not having enough space for them, so I want the retained copies to have a quality as high as possible, which leads to multi-GB file sizes.

LTO-5 worked great for my use case and I find new/old-stock LTO5 tapes for about $5/TB on ebay. I verify every tape after writing, and I include about 25% to 30% parity data on each tape to combat bit rot. I don't really need to write more than 1TB at a time of data, and the rest of the room on the tape is parity data (PAR files).

The drive was super cheap, $150 used. I don't expect it to last forever, I plan to buy another tape drive as a backup and eventually upgrade to an LTO-6 drive.

After making 2 copies of all my important data, about 30TB on LTO-5 tape, I don't have that much to back up, maybe 2TB a month, but it's easy to justify buying a few more tapes every now and then. Buying 2 hard drives for redundancy is just not anywhere near as cheap as buying 2 LTO tapes for the same amount of data, even for people with less than 100TB of data.

It’s like saying “hard drive platters are really dense storage and super cheap” and ignoring the cost of the actual drive itself