I can buy an 8 core AMD Opteron for $18 with shipping on eBay, so actually I can get 128 cores of x86 for $288. Checkmate lazy journalists.

Proof: https://www.ebay.com/itm/234113546803 and that's just the first result when I searched AMD Opteron. I didn't even bother to see whether I could do better with other old CPUs.