It’s a bit hard to tell, since not every Firefox install necessarily corresponds to a single user, but it’s probably in that ballpark: the number of active installs is hovering around 200 million.
Don’t underestimate the size of the browser market. A small share of a market of a couple of billion users is still a lot of people.
And presumably, like everywhere, not every dollar automatically makes things better, but having to pay people to do stuff like this isn’t cheap.






I think it’s just a preview feature, so it’s not accessible through a normal menu yet I think, but if you type
about:keyboardin the address bar and press Enter, I think it will allow you to remap these (under the Navigation section).