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Just checked and they charge $0.015/GB/Mo -- outrageously expensive and way way over the competition which is charging from $4/TB/Mo and up (ie, $0.004/GB/Mo, less than a third of rsync.net's price)
Backblaze B2 too
Already covered and discarded as too expensive, but thanks.
There are also workarounds like using a private telegram chat or files encoded in unlisted YouTube videos, but those are much harder to automate.
The worst part of these "workarounds" IMHO is unreliability, and this misses the whole point of cloud storage as a backup, because when accessing a backup is needed, it's really needed -- failure is not an option at all.