Intel Xeon E5-2665 ($80 on eBay) = 8 cores, 2.3-3.1GHz
Intel Xeon E5-2660 ($60-65 on eBay) = 8 cores, 2.2-3Ghz (so you can buy two for $120-130)
Intel Xeon E5-1650 ($97 on eBay) = 6 cores, 3.5-3.8GHz
E5-2665 beats FX-8350 hands down, and is cheaper.
I can buy a whole workstation with E5-2665, motherboard, 32GB RAM, 1TB HDD, all for $414, shipped.
http://www.ebay.com/itm/162274529994
I doubt you can find something like that with FX-8350 and cheaper. And it will still be slower.
Depends a lot on your electrical cost. Some people live in places where the power costs $0.05 per kWh. Some people live in places where it cost $0.36 per kWh (Hawaii).
If somebody wants a machine with a lot of xeon cores and a ton of ram (but noisy), you can buy a dell poweredge r910 server with 4 sockets x 8-core xeons and 128GB of RAM for like $1100. Makes an excellent xen or kvm hypervisor dom0/host development machine. It's just noisy, so in a home environment, put it in your garage or something on the far end of a cat5e cable.
I have a AMD FX 8320 workstation, and I assembled it brand new for less than €400.
In fact, if you take away the €130 referring to the price of an AMD FX 8320, you get the remaining budget for the mobo, RAM, and HDs.