It's not exactly cheap to always have a backup that you know works. You have to set it up and test it periodically. Of course, that doesn't mean you shouldn't do it.
Very much that. As a former SRE responsible for tape storage, I saw things like regular backups of an error phrase "You have no access to this database". Guess what happened when the team accidentally dropped the database?
Unless you're doing regular restores, you don't have a backup. You have hope. So yes, doing backups in a way that gives you some form of guarantee isn't exactly cheap.
Or we do have everything in the backup, but the restore process isn't worked out. Someone is losing a weekend writing hacky scripts, and every SLO is being violated, if we ever have to use it for real.
Unless you're doing regular restores, you don't have a backup. You have hope. So yes, doing backups in a way that gives you some form of guarantee isn't exactly cheap.