I think it's the 2680 or 2690. Intel Ark will tell you
The E5-2660v4 is about £1200.
The E5-2680v4 is about £1500.
A SuperMicro DP 2011 board depending on features you want will set you back about £400.
Seems pretty much the same ball park totals as the 6950x and a decent X99 board (for a single CPU setup, its considerably more once you start talking dual CPU).
Even if I go down to some of the older v3 Xeon's for a 10c/20t at around 3Ghz you are still looking at over £1k.
It's horses for courses.
There seems to be a lot of salt in this thread and I'm not really sure why. What were people expecting? I think the BW-E line up was always going to appeal to a niche audience, the same as the Xeon's do (outside of business and servers) in the retail market.
People that want them will buy them and enjoy them, when the next big thing comes out they may well buy that as well and then this generation will float around the second hand market and many people might get a bargain in a number of months time.
I fail to understand the overall negativity.