You are kind of glossing over the B2B market where contract pricing is basically just MBA vibes and the fact that people don't really care necessarily about the performance of the language model once it hits a baseline. They care about how it integrates into their lives. Precisely where first mover advantage comes into play. Having to train a language model all over again is it's own sunk cost.
B2B absolutely cares, especially since ZIRP is unlikely to ever come back in our lifetimes. No sane corporation is going to continue to throw billions down the drain with nothing to show for it.
b2b needs actual ROI and that's no where near. CEOs would be yelling loudly if this were returning them cash instead they're just jettison people to afford the bills.
OpenAI themselves said, in their revenue projections, that they expect the consumer vs enterprise revenue split to be 50:50, though — see:
https://news.ycombinator.com/item?id=48451053