I get different numbers. First, it was 6,500 CPU core-years comparable to a relatively recent Xeon that uses about 10.5 watts per core. So, 57 million cores, 60

I get different numbers. First, it was 6,500 CPU core-years comparable to a relatively recent Xeon that uses about 10.5 watts per core. So, 57 million cores, 600 megawatts, and about 11,000 racks (if you can fit 128 * 42 equivalent cores per rack). Wholesale electricity is about $50/MWh, so $30,000 for the CPU part. The numbers they give for the GPU part are more confusing, and despite the time difference, they say it was the more expensive phase of the attack. However, it appears to involve considerably less physical hardware. Still pretty impractical for what's probably limited value, but not out of reach.