I wonder why they haven't tried that yet:
Firefox Support Edition, for $10 a month you get nothing (or maybe some Sync stuff) but all the funds go to Firefox exclusively, and your copy will show a pretty star on startup or something else.
Patron Edition: for $20 a month, same thing but you also get the VPN from Mullvad.
160M users. If 10% subscribe, you get $160M every month. I'm a marketing genius.