Disclaimer: I work at Backblaze. Here is a histogram of backup sizes of our Backblaze Personal Backup Customers if it is useful:

https://i.imgur.com/GiHhrDo.gif

You have to zoom in to see the meaningful information. It can be super surprising to developers and IT people (like us) to see a lot of customers have less data than you might think.

When we started we had no idea what might come of all of this, so it was "stressful". :-) So I welcome another backup client developer to our club, and hope this can help them out.