True, Tarsnap is pretty on-point there, but it's also not cheap. $0.25/GB is much more than S3 ($0.023) or B2 ($0.005) - the tarsnap dev says it's because he does blocking and that makes it so much more valuable. But and there are other tools that can do encrypted backups with blocking like Duplicati and can be used with cheaper services. With this considered, Tarsnap is 50x the price of B2 - and that's without counting bandwidth.
Or if you're a cheap fuck like me, you want even lower and you go to OVH Hubic which is $50 for 10 TB for a year, with no additional bandwidth cost.
Previously: business use typically comes with expectations that tend not to align well with consumer grade products (specifically: availability and performance).
Edit: Turns out the answer is yes, no commercial use.
1.2 Using Your Files with the Services. You may use the Services only to store, retrieve, manage, organize, and access Your Files for personal, non-commercial purposes using the features and functionality we make available. You may not use the Services to store, transfer, or distribute content of or on behalf of third parties, to operate your own file storage application or service, to operate a photography business or other commercial service, or to resell any part of the Services.
True, I guess it's seemed cheap to me because I store relatively little data on Tarsnap. (In fact, I don't think I've added any funds to my Tarsnap account in like 2 years.) If you're dealing with larger quantities of data I could see how other options would be the way to go.
Or if you're a cheap fuck like me, you want even lower and you go to OVH Hubic which is $50 for 10 TB for a year, with no additional bandwidth cost.