Way back when 2008 saw the release of Iron Man, Marvel had placed all their hopes on a single, second-string character (as far as pop culture was concerned). A director with a mixed record and an actor primarily known for his legal woes and drug use led the film, and which was
a self-funded production. While Paramount studios would distribute, Marvel remained an independent studio, fueled by profits gained by farming out characters like Spiderman and the X-Men to other studios. Marvel accomplished this feat by keeping the budget under control.
Then Disney took over, and all the ills of the Hollywood studio system seeped into every production. Salaries skyrocketed, as did "talent perks" like profit shares from merchandise which caused budgets to swell. Now, what began with Iron Man costing $100-140 million, has begat Avengers: Infinity War, already estimated to cost $1 billion!