I got these cheapish from ProVantage.com . I saw that price a couple of times before I pulled the trigger. They seem to sell out within a day. I say cheapish because I see RDimms for less than $70 sometimes, but the udimms were $180 each less than six months ago.
KIN93CU 4x KSM26ED8/16ME. Kingston Technology 16GB DDR4-2666 ECC Unbuffered DIMM CL19 2Rx8 1.2V Micron E Die (Server Premier) @ $81.94 each
Warehouse confirmation received.