I feel your posts miss the bigger picture: it's a marathon, not a sprint. If you get much lower TCO than by buying Nvidia hardware at their insane margins you get more output at lower cost.

Amazon has all the resources needed to write their own backends to several ML software or even drop-in API replacements.

Eventually economics win: where margins are high competition appears and in time margins get thinner and competition starts disappearing again, it's a cycle.