Not the highest performing thing around, but hard to beat at $100. It is listed at $125, however the seller has already sent me an offer for $100, so I'm sure they will accept if you submit one with the same amount.
SuperMicro X9DRL-iF, LGA 2011/Socket R, Xeon e5 2620v2 And 64gb Ram 672042106899 | eBay
SuperMicro X9DRL-iF, LGA 2011/Socket R, Xeon e5 2620v2 And 64gb Ram 672042106899 | eBay