OpenAI's recruiting pitch was 5-10+ million/year in the form of equity. The structure of the grants is super weird by traditional big-company standards, but it was plausible enough that you could squint and call it the same. I'd posit that many of the people jumping to OpenAI are doing it for the cash and not the mission.
https://the-decoder.com/openai-lures-googles-top-ai-research....