That's cheap indeed. Enough headroom for some failing disks too. How is the noise and power usage? I didn't look at SAS drives at all, because my impression was that they're very noisy. I can place my NAS in a closed off room, but it's not too far away and I was afraid SAS drives would be audible through the wall. At the same time, the shucked drive I'm using presents itself as an WD Ultrastar, which comes very close to a SAS drive, and isn't very noisy.
I think they're same as SATA drives, just different interface. AFAIK they have the same physical dimensions and same internals.
Also something people forget for home nas or figuring out cost for a nas, the power draw of the entire system times your electricity price you then have to multiply this times 2x to 4x times if your climate requires cooling air conditioning of any kind