They are doing R&D. I don't know what their other projects are. Most of their $12B in annual revenue is coming from GPT-5, so if we take your $2.7B figure for training GPT-5 at face value they have most likely already paid it back. If you figure GPT-5 is around for 6 months... the economics are straightforward.
Yes employees but the employees are working on R&D. I'm not saying all of their R&D is good, only that GPT-5 is clearly a profitable product, same as Gemini and Claude.