I have a feeling many of these will reappear on ebay at a higher price. I already see ConnectX3-EN at $85 that I didn't before. Usually it is the VPI/Infiniband with QSFP variant that is sold at bargain prices not the ethernet SFP+ model.
Got one of these last week at this price via auction though.
They pop up from time to time.
Mine showed up today (its very small), has a 1/2 heigh bracket, so now off to hunt for a full height bracket.
The Mellanox store wants $16 to ship a $4 bracket lol, i say no.