I think his main point was cost savings in environments that don't need constant uptime, like Dev and QA DB's in a 9-5ish shop.

You can also throw a light DB (mySql, SqlExpress, Postgres) on a VM that you already have running 24/7, that would make the additional cost zero.

Of course you are still going to need to curate your dev/qa data (through replication or periodic backup/restore) because shit data is hard to code against, not to mention debug against.