If most of their employees live in high COL areas like Mountain View, CA, then the 200K figure seems very fair. Maybe even low.

They don't appear to, however. For another response, I was looking at their 2019 financials, and for the Mozilla Foundation unit, 60 employees cost about $11M. I stand by my guesstimate of $200,000 as a high estimate.

I expect the foundation (which is largely non-technical) to have much lower average compensation than the corporation (which is predominately engineering-focused).

That 11M would, however, cover a lot of the leadership and directors, who are among the highest paid employees of the company.