How quickly do you need to be able to restore? Is it commercial or homelab?

The most cost-effective option by far would be to put a NAS device someplace offsite. You could use tailscale to connect to it remotely.

After that, depending on your access patterns, either a glacier-style s3 service (aws or backblaze/etc), or a rented bare-metal server with big disks some place inexpensive.

You can probably get away with google drive+rclone+borg/restic/whatever, but it will be rather clunky. Backblaze might be a nicer backend to use.

I use rsync.net with borg, but not sure about your budget. Their 1TB lifetime plan is very competitive though.