I have not seen any of the employee contracts so this is purely an educated guess which might be entirely wrong. There is a chart from Fortune[1] that spells out how the profit caps work. I have not looked at any of the documents myself so I am interpreting only what I have consumed. My guess is that the employee equity/contracts spell out the cap structure so perhaps the equity value is based off those caps. Assuming the profit cap for employees is correct I would assume you could not value any "equity" based off the last raise value. At best you could perhaps value the max cap available for those shares.

[1] https://fortune.com/2023/01/11/structure-openai-investment-m...