If compression is purely a function of the price, things are not so obvious.
I think Backblaze B2 is the cheapest, but it's not supported by Borg. So a backup system without compression support, but with B2 support, may ultimately be cheaper than a system with opposite features.
It's also important to consider the use case. If a user's bulk of data is photos/videos/audio files, there's virtually no use of compression - but of course, the proportion will vary per user.
I’m using restic too for part of my backups, having moved from duplicity. My experience has been (on a dataset which is relatively compressible ie not audio/video files) that deduplication has saved me quite a lot more space vs duplicity than I lost through not having compression.