Yes, but how large is the subset of Firefox users that are willing to pay for a browser? Take that number and multiply it either by 10 o by 100 and you get the order of magnitude.
a) It’s insane how little we pay for browsers given their utility.
b) Many people would be happy to pay extra for a browser to support free access for others (The Guardian was a decent example of that IIRC).
Going by the 2023 financial report (getting the 2024 report requires to submit a mail address?!), Mozilla spent over 500mil in that year, 328m on salaries (page 5).
I googled this https://www.reddit.com/r/firefox/comments/1mhks3h/firefoxs_w...
Let's say we are at 100 million users. If only 1 out of 100 pay, it's 10 to 100 million dollars per year. A lot of money or a puny amount, it depends.