Your brain is analog. Trying to emulate this with a digital computer is bound to come with some computational cost.
Good thing we aren’t trying, then. GPT works in a completely different fashion.
The world created by human thought has given us such excess means of power production that we have literal gigawatts of electricity we can use in a trade off where it doesn't take us 4 billion years to make efficient circuits.
Maybe superintelligence isn't possible for some reason, but the fact we exist should tell you that general intelligence is not magic.