why this cost 50m+ ?

Zendaya’s salary alone cost them $10 million

I hear the tennis scenes were laborious and probably expensive . New York Times reported that one 10-minute tennis scene took 8 months to do because they wanted to arrange shots at certain angles, like under the net and right behind / above/beneath the ball. The actors/actresses didn’t actually know how to play tennis at that elite level, so they had to use CGI. They had the actors swing the racket handles into air, and CGI plugged in a ball and racket