One use case: I don't like the idea of having any accounts at all which I log into without the aid of a password manager. That creates a bootstrapping problem - how am I supposed to log into Google Drive to get my Google Drive password? A prepaid keyfile-based model is one particularly robust way of solving this. You stick your e.g. 100 kB password database in there, print out and shred the keyfile, stick the printout in a fireproof safe, and be virtually certain that whatever you put in Tarsnap has been untouched however many years you come back to it later. Print it on archival paper with some silica gel packets and it might survive for millennia in your weird subterranean vampire family castle.

"The business won't survive that long." I'm not so sure. Its ongoing costs appear minimal, and it generates eye watering amounts of float. $5 paid today is >$200 fifty years from now when compounded at 8% real interest. That very fact makes it much more likely that Tarsnap actually will survive for those 50 years, which should make us more likely to trust it, which... You see where this is going. This is one of those things where aggressively pricing too close to the bare metal costs might actually be a bad thing to a very important subset of users. One might even make the argument that, if the margins are as good as I'm supposing they are, then depending on the goals of the founder, Tarsnap is more likely to outlive S3 than S3 Tarsnap.

But again: Primarily a hobby.

[1]: https://andrew-quinn.me/digital-resiliency-2025/