I doubt many (any?) startups would match FB's 10-year senior engineer's total comp. That would burn up the startup's cash (and/or ownership) very quickly.

I think the main draws at a startup for a post-FAANG senior engineer are feeling good about the product they build (more useful to the world than FB's ads) or the role/environment (less bureaucracy and org process). I am sure there are many exceptions, but I suspect that after 10 years in a senior role at a FAANG money stops being the most important thing you need from a job. My 2c.