The fact that there’s this much browser diversity is great. These alternative browsers are able to experiment with their approach and appeal to a passionate enough user base that keeps them going. And if these features do work, the mainstream browsers end up adopting them in future versions.
Nearly all, if not all, browsers are free. This is all happening due to the wonders of the modern web. The mainstream browsers have huge corporations supporting their development. The others support themselves through advertising by selling the search bar to search engines. I don’t know the how much revenue the average user makes or how many users it would take for a browser to stay alive but the more we experiment with these alternative browsers and try them out the healthier the browser ecosystem.