That's fine, because you don't need infinite compute to run or train current models. If the "big boys" are buying more compute that's because they hope to provide a better service.

I misspoke when I said "zero". I should have said "down to marginal cost". It's fine for AI to be priced at the cost of its compute! That's the efficient outcome.

What reason do you expect to provide a moat for a monopoly? Training on existing customer interactions? That might get you an oligopoly, but there are already two serious competitors in the US alone and several potential Chinese rivals.