Marvel Cinematic Universe movies earn billions of dollars, so you'd think the creators of the characters and storylines they depict would be swimming in dollar bills. Not so, according to a new report from TheGuardian, shining a spotlight on writers fighting to be fairly compensated by Marvel.

"According to multiple sources, when a writer or artist's work features prominently in a Marvel film, the company's practice is to send the creator an invitation to the premiere and a check for $5,000," The Guardian reports. "Three different sources confirmed this amount to the Guardian. There's no obligation to attend the premiere, or to use the $5,000 for travel or accommodation; sources described it as a tacit acknowledgment that compensation was due."

The report said Jim Starlin, who created Thanos, "negotiated a bigger payout after arguing that Marvel had underpaid him for its use of Thanos as the big bad of the MCU." Roy Thomas, who wrote prolifically on Marvel's X-Men and The Avengers, "got his name added to the credits of Disney Plus series Loki after his agent made a fuss."

Attention was first brought to the issue in late March, when comic book writer Ed Brubaker published a newsletter about his "mixed feelings" when it came to Disney Plus series The Falcon and the Winter Soldier.

"For the most part all Steve Epting and I have gotten for creating the Winter Soldier and his storyline is a "thanks" here or there, and over the years that's become harder and harder to live with," Brubaker wrote.

Brubaker, who created The Winter Soldier character in 2005 with artist Steve Epting, added that the compensation situation made him feel "sick to [his] stomach."