I must be lucky then finding working SCSI 50 pin HDs for next to nothing. it might be because I am always on the lookout for cheap consumables for the hobby (and HD's and floppy drives are consumables because of moving parts). If you are going to look when you actually need a replacement drive then you are stuck with whatever is around at the time.

I lucked out years ago and purchased a whole box of 1 or 2GB 50 pin drives NOS (20 pcs) most with 0 hours and they work fine (price was $15 or 20 forget which). Even the used drives I find seems to be reliable, and I do test them for any bad sectors and dump the ones with any bad ones. I stocked up on old IDE drives for my old PCs from arecycler and paid something like $2 a drive that I kept (the bad ones went back at no charge). Stocking up on IDE laptop drives now as well (having a large laptop collection mans having tons of spares).

I have yet boot up a machine I redid and have the HD go bad. Some machines sit for a year before I get back to using them but none are stored where the temperature and humidity goes crazy up or down.