50% directly spent on Firefox development.

12% spent on marketing (for comparison, rumor has it that Chrome's marketing spend is comparable to Mozilla's total revenue).

13% general and administrative expenses (this includes things like leases on office space, as far as I can tell from the usual definition of this category).

9% (of revenue; it's 36% of profit) income taxes. Which Mozilla apparently pays, unlike some other tech corporations.

16% money going into the rainy-day fund.

Disclaimer: I work for Mozilla; pardon my snark about taxes. It's a sore point.