This is 4-8 cents per GB-month, with no transfer fees. Tarsnap is 25 cents per GB-month, plus transfer fees.

That's for Tarsnap's encoded data---but that seems roughly comparable to rsync.net's free snapshots. So Tarsnap is something like 5x the cost.

For that 5x cost, you get secrecy of your data (but not your connectivity, metadata, backup schedule) from your backup provider.