PHOTOS: 'Avengers' Premiere: Red Carpet Arrivals

According to multiple knowledgeable sources, Iron Man/Tony Stark is set for a highflying payday of about $50 million once box-office bonuses and backend compensation are factored in. (Two sources claim the number could go higher than $50 million once the ultimate box-office haul of Avengers is known, but another cautions that it could be years before the final number is known.) While on par with the upper echelon of franchise movie stars, that number blows away his superhero co-stars, all of whom will make a small fraction of Downey’s total, even as Avengers has a shot at topping the final Harry Potter film’s $1.32 billion global haul.

Why the difference? When Marvel’s Iron Man grossed a surprising $585 million worldwide in 2008, Downey’s reps at CAA and the Hansen Jacobson law firm renegotiated a deal to include what multiple sources say is a slice of Marvel’s revenue from future movies in which he plays Iron Man (one source puts it in the 5 percent to 7 percent range; another source disputes the percentage. Marvel and Downey’s reps declined comment).

As Marvel launched other hero pics that would lead up to Avengers, the studio struck hard bargains. Two sources say Chris Hemsworth, Chris Evans, Jeremy Renner and Mark Ruffalo all signed on for small upfront fees and ultimately will make about $2 million to $3 million on Avengers with bonuses. Samuel L. Jackson and Scarlett Johansson, who signed deals to pop up in several Marvel movies, are said to be making about twice that for Avengers with bonuses.

Avengers has become a global goliath, passing the $1 billion milestone in just 19 days. If it passes the $1.32 billion of 2011's Harry Potter and the Deathly Hallows Part 2, Avengers would become the third-highest-grossing film of all time, behind only James Cameron's double-whammy of Avatar ($2.8 billion) and Titanic ($2.2 billion, including grosses from the recent re-release). The Marvel film is distributed by Disney, which purchased the independent studio in 2009 for $4.3 billion.

While Downey’s pay might seem high, it's not unheard of for stars with backend to collect super-rich paydays when their films become global smashes. Johnny Depp is said to have made at least $250 million from the four Pirates of the Caribbean movies, and Forbes reported that director Michael Bay took home $80 million from the first Transformers. (He likely made more than that for the sequels.)

At those rates, Downey almost seems cheap.

Email: Matthew.Belloni@thr.com

Twitter: @THRMattBelloni