I pay around £70 a year for the Syntology C2 service (released with DSM 7.0). We don’t back up individual machines, but we do (either automatically or manually) copy everything we really care about (including our limited company stuff) onto our basic 2 bay (mirrored) NAS.
It’s only 1TB, but that’s enough for the data we really care about and includes the time machine backups from my Mac. So in terms of the standard 1-2-3 backup, we’ve gone for.
1- all our most important / not backed up elsewhere data on the local NAS
2- NAS backed up to Syntology C2
3- iCloud enabled for all my work/personal data
4- OneDrive used randomly by other family members
We run two factor everywhere for the NAS/backup and I don’t let the Syntology client work through the firewall. If I need data desperately I just get someone to email it to me (I think I can get it off the C2 server as well)
I’m probably as worried about ransomware as I am about disk failure. For £70 a year, it’s piece of mind.