The pair starred as detectives in the thriller, which was released last year.
Miller told Empire: "Everybody understands about the pay disparity in Hollywood, but I asked for a number that the studio wouldn't get to.
"And Chadwick ended up donating some of his salary to get me to the number I had asked for."
She added: "He said that that was what I deserved to be paid."
Black Panther star Boseman, who died of cancer earlier this year, was also one of the film's producers and had pursued Miller for the role of Frankie Burns.
