$3000 per TB-year is accurate to my knowledge, and yes, it is at least one, and probably two, orders of magnitude what you can get with more general purpose systems. Backblaze B2 is $72 per TB-year; AWS Glacier is $12 per TB-year I believe; purchasing two 20 TB Seagate drives for $300 apiece, mirroring them, and replacing them every 3 years gives you about $10 per TB-year (potentially - most of us don't have 20 TB to back up in our personal lives). Those are the best prices I've been able to find with some looking [2].
To me, when I was building out the digital resiliency audit, the pricing and model just seemed to tell me that tarsnap was for very specific kinds of critical data backups, and was not a great fit for general purpose stuff. Like a lot of other people here I also have a general-purpose restic based 3-2-1 backup going for the ~150 GB in /home I back up. [3] My use of tarsnap is partly a cheap hedge for the handful of bytes of data I genuinely cannot afford to lose against issues with restic, Backblaze B2, systemd, etc.
[1]: https://hiandrewquinn.github.io/tarsnap-calculator/
[2]: https://andrew-quinn.me/digital-resiliency-2025/#postscript-...
[3]: https://andrew-quinn.me/digital-resiliency-2025/#general-bac...