I wonder how much more you pay in electricity costs over a Kaby Lake 7700K for example, which idles much lower and wouldn’t need to overclock.
Anyway, the machine runs an, admittedly overkill, GTX 1070 with a TDP of 150W, so the CPU power usage is the least concern.
Also, since CPU's are idle more of the time than under load the savings by using a newer CPU like Kaby Lake or Ryzen could be interesting. There is also the motherboard. Newer boards consume less power because the chips are on a smaller node.
But I guess the money you saved on buying the CPU will outweigh the electricity costs even in countries where electricity is expensive.
Unless he's running 24/7 and paying way too much, yeah, by a large margin. Even these older Xeons weren't that bad at energy saving.