> At their scale they will never be able to use anything else than a cloud solution.

That's definitely not true, and there are many companies doing higher volumes at a fraction of the cost-per-query.

Although scale doesn't force companies into public-cloud database systems, considerations like capital, time-to-market, and business strategy often do. In this case, OpenAI is trading a significantly higher per-query cost for benefits like improved agility, turnkey compliance, etc.