Tilly2:
In the very early days of the internet a few companies tried to sell their web browsers. Some also took legal action against Microsoft to try to prevent them bundling Internet Explorer with Windows, as it greatly reduced the chances of any other company being able to sell their own browsers. (Microsoft actually lost such a battle in the European courts. To this day they're legally obliged to offer Windows, at the same price as they'd normally charge for it, without any browser included if a customer demands it).
However companies making web browsers eventually gave up on trying to sell them and either stopped producing them altogether or made them free (and sought other ways of making money instead). Also some people decided to create 'open source' browsers just for the general good of internet users. So now all browsers are free. (That's true for PCs. There might be some for Android devices, etc, which are charged for, but I'm unaware of any)