My current setup is eight 18TB Exos drives, all purchased from Amazon's refurb shop, and running in a RAIDz2. I'm pulling about 450MB/s through various tests on a system that is in use. I've been running this about a year now and smartd hasn't detected any issues. I have almost never run new drives for my storage and the only time I've ever lost data was back when I was running mdadm and a power glitch broke the sync on multiple drives so the array couldn't be recovered. With zfs I have even run a RAID0 with five drives which saw multiple power incidents (before I got a redundant power supply) and I never once lost anything because of zfs' awesome error detection.
So yes, used drives can be just fine as long as you do your research on the drive models, have a very solid power supply, and are configured for hot-swapping so you can replace a drive when they fail. Of course that's solid advice even for brand new drives, but my last set of used drives (also from ebay) lasted about a decade before it was time to upgrade. Sure, individual drives took a dump over that time, this was another set of eight and I replaced three of them, but the data was always safe.