We do a two tier approach to backing up sites:

1. We have our hosts back up our servers daily to a local store.
2. We run a system that grabs all files and the DB and keeps a copy on our office server.

For number 2 you can use custom scripts of systems like SiteVault. Either way, the costs quickly come down.

VaultPress is terrific value if you have one or two sites on WP. But if you have a lot of sites it does look rather expensive. It's also time consuming if you need to repair a large multi-sites instance of WP.

The other big advantage of VaultPress is that it requires few skills to work with, whereas our approach demands some understanding of servers, hosting and DBs. That knowledge costs money. We have it, but some people don't - for them VaultPress is a sweet solution.