Backing up an on-prem DB doesn't require specialist DBA knowledge. Basic UNIX skills are enough. Not to mention, since you're not in the cloud, bandwidth or efficiency is not a concern - feel free to rsync your entire DB off to a backup server every 5 minutes.
> to hire a rock solid DBA? And how much does that DBA cost?
They didn't have a DBA here either, and this "cloud" didn't save them. But at least with an on-prem Postgres the worst they'd have is significantly reduced performance*, where as here they had a 5k bill.
*actually the price/performance ratio for bare-metal servers is so good that a 100$/month server would probably take their unindexed query and work totally fine (as a side effect of the entire working dataset being in the kernel's RAM-based IO cache).