This reasoning about the subscription price etc is undermined by the actual prices OpenAI are charging -

The price of a model capable of 4o mini level performance used to be 100x higher.

Yes, literally 100x. The original "davinci model" (and I paid $5 figures for using it throughout 2021-2022) cost $0.06/1k tokens.

So it's not inverting in running costs (which are the thing that will kill a company). Struggling with training costs (which is where you correctly identify OpenAI is spending) will stop growth perhaps, but won't kill you if you have to pull the plug.

I suspect subscription prices are based on market capture and perceived customer value, plus plans for training, not running costs.