Hypothetically with 256 megabytes of L3 you could also have a 128 thread monero miner.
My extrapolation from the 3970X (28900 hashes/second x 2) = 57800 hashes/second x 0.9 (due to scaling not being completely linear due to lower clock speeds) = 52020 hashes per second
Putting that into a monero calculator with a 300 watt power drain for the system and 0.06 Cost per KWh we get $1,364 profit a year.
$3990 / $1364 = 2.9 years to recoup your investment.
Comparing this to a Geforce 2080Ti we get a strangely similar 2.89 years to recoup its investment.
$1300 / $1.23 a day = 1057 days / 365 days = 2.89 years
With the 3950x clocking higher and being 35% cheaper per core it would make more sense to use 3 - 3950x in 3 separate rigs than a 3990x.