I'm not very familiar with the business of tennis specifically, but in sports in general a plurality or even a majority of the money comes from advertisers who

I'm not very familiar with the business of tennis specifically, but in sports in general a plurality or even a majority of the money comes from advertisers who pay to sponsor events or show ads on the TV broadcast. The rates for those ads depends on the ratings and popularity of the event. The next biggest chunk of money is directly from fans in the form of tickets, merchandise, and directly paying to watch through streaming or pay-per-view. Some of these journalists work for the TV networks that use those ad dollars to pay the league, organizers, and athletes. Some of those TV networks have contracts guaranteeing them access to the athletes for pre/post game/match interviews and other appearances, but the primary product they are purchasing is always the rights to broadcast the game/match itself because that is what gets the biggest ratings and the biggest ad dollars. Many of these journalists work for some other media company that is not paying anything beyond just the general promotion of the sport. So "the media pays the athletes for these interviews" is only true in a relatively lower dollar amount and in a rather indirect way. Nowadays these journalists need the athletes more than the athletes need the journalists (this shifting power dynamic comes with its own set of problems, but that is a different conversation).