Earlier quoted context omitted.
It does not have to be the majority. It would suffice to produce enough funds to continue developing Firefox, with full-time engineers, infrastructure, etc. The whole Mozilla foundation budget oscillated around $100-120M/y for last few years. Let's assume that half of it was dedicated to Firefox; e.g. $60M/y. It would take 500k users paying $120/y (aka $10/mo) to support their favorite browser. The current audience o…
> The whole Mozilla foundation budget oscillated around $100-120M/y for last few years. Firefox is under corporation, not foundation. Mozilla Corporation expenses are $400M+, not $100M. https://en.wikipedia.org/wiki/Mozilla_Corporation#Finances (I don't enough knowledge about freemium economics to figure out if the stated numbers would work out or not)
If we adjust to these numbers, we need to quadruple the number of paying users, up to some 1.2% of the total user base. Let's add a safety margin, and bump it to 2%.
Still does not look impossible to attain.