Agree, but that's taking a risk with your data (whereas if a MB fails, you likely just need to replace it but your data is fine), and HDD kind of have a finite number of hours in them. Where buying them used I think makes sense is for a backup server, that you leave off except the few hours in a week where you do an incremental backup. Then it doesn't really matter that the drives have already been running for 3 or 4 years.