Whenever there are movies that are being produced, those in the movie industry may choose to gamble or to think about the prices of producing the movie. If the movie is a sure hit, they know that they would make more money than what they have previously paid for it. There are times when the capital for movies is very high but for different reasons, the movie bombs at the box office.
This can mean losses for the company. There are also times when it can be the opposite. Those producing the movie did not even spend too much money but the movie becomes a hit. Creating movies is like taking a gamble. You sometimes do not know what you will get.
The simple answer is that the movie industry earns so much capital because once the movie has been filmed and released (which costs a lot of money by itself), every time the movie is played in a theater or on television, the movie earns more money. So if you consider a theater actor or actress, they can only earn the money from the people attending the shows at one theater at a time.
They have to keep performing the play or act over and over again in order to earn more money. With movies, they release the film nation wide and even world wide and each time that happens, they earn more money. That does not even take into consideration future revenue of allowing a Streaming service to show it or DVDs of the film.