The price for $10 was as countzero said only if you bought a count of 10. I expected to do this a lot since I have quite a few older scsi based machines (Amiga, NeXT, SGI, Classic Mac, etc.).
I have a couple of ACARD units which are cool but definitely are more expensive. The R-IDSC-E/R that was covered in the link I supplied above were the ones I got for a significantly cheaper price.
The jumper settings are important and you should check out the link if you have one to make sure you have all the settings correct.