I don't think you can, and such a comparison is not really needed here anyway. People are not chattel slaves and cannot be racked into data centers to solve boring problems.

Of course, you can hire people, and that has a well-defined cost, so it does all come down to money again.

Sure, but the whole point of the above idea is to compare our 20W computers to what we can build that eats 20W. And don't give Silicon Valley ideas about disrupting the lucrative Mechanical Turk ecosystem by scaling it up with ideas borrowed from growing veal because some VC sociopath will take it seriously. Just sayin'...

And I'm saying that this 20W limitation isn't particularly meaningful, as many organizations have way more power at their disposal to throw at a problem than that. The economics of a given solution, on the other hand, is applicable at all scales.

Meaningful in the sense that if an AI plays against humans, is it smarter at the same energy efficiency of humans.

We are comparing machine intelligence vs human intelligence.

It can be said that with more computational power, you can raise intelligence. Human brains consume the most power relative to body size than any other animal.