Yeah, IMO if you want a rough idea about how much compute the human brain performs, and how efficiently you could do that in silicon, it's interesting to look at area V1 which is one of the lowest level areas involved in vision. This brain area comprises 140 million neurons per hemisphere (so roughly 280 million in total). So that's about 1/300 of the human brain.

The interesting thing here is, what V1 does is it computes directional receptive fields based on raw data from the retinas. We can implement that in a tiny silicon chip, maybe even just a DSP chip, not a full CPU. We know how to implement this kind of computation super efficiently, and without using neural networks.

We don't fully understand what goes on in many areas of the brain, but if we can find efficient ways to implement equivalent computations, we might technically already have sufficient manufacturing technology to implement equivalent functionality in a pretty compact and power-efficient form factor, or we might not be that far from there.

A classic quote from Dijkstra: "The question of whether machines can think is about as relevant as the question of whether submarines can swim."