If Hetzner storage boxes work for you, that would be less than 4 euros per month with unlimited traffic. Next level up is 13 euros for 5TB. (It works fine with restic over ssh but also has options for samba, webdav etc in addition to borg server. Now that I am looking at the info page, it seems restic is listed now too but I am not sure if it's via rclone . https://www.hetzner.com/storage/storage-box )
https://www.backblaze.com/cloud-storage/pricing
$6/TB/Month. Very manageable egress-fees. If you're using it for cold-backup, hopefully you rarely have to pay them.