I picked up a refurbished 12TB hard drive on eBay from goharddrive. I've seen a lot of these deals lately. They are supposedly used in datacenters and are being cycled through. For $80 I figured it's worth the gamble.
These have the Power Disable feature, so they don't boot up on a regular system. Fortunately, the seller provided a SATA power adapter that works around the issue.
I think it said that these drives were in use for up to 5 years. The SMART data on mine says about 500 days of use. Others have reported much longer use so I seem to have got lucky, at least on that part.
Now I just need to acquire enough porn to fill this drive.