Models cost a ton of money to train. GPT-4 training was > $100m. GPT-5 training is estimated to be order of $1B-$2B. This is in the same ballpark as Tesla allocated to get the Fremont facility online.

It is likely training generations beyond GPT-5 will cost still more.

These are essentially fixed costs as OpenAI has to pay to train the model whether or not anyone ever uses it.