Have you ever bought a targeted ad? It costs money for corporations to collect and maintain databases of user information. They go to the trouble because they can profit by responding to customer demand for personal user data. Google and Facebook are mainly in the advertising business.
And that business is profitable through monopoly power. If customers could pay what advertisers pay for Google and Facebook not to track them, the entire model would collapse. Google Adwords averages about $115 CPM. Google has analytics on all of this. Google could charge me 11.5 cents for every ad they're not showing me - at which point I would look at the pathetic amount of money Brave throws at you for opting into the BAT platform and either accept that my searches are worth a dollar a day or recognize that my privacy is worth more than that. The power of the transaction is in the opacity.