casting - Why didn't Katie Holmes play Rachel Dawes in The Dark Knight?

According to Julie Polkes, a spokeswoman for Ms. Holmes,

"Katie was offered but was unable to accept the role because of
scheduling conflicts. She was in the process of negotiating for
another project. In addition, when she returns to work, she would like
to tackle a new character."

But according to this article,

The studio is searching for a new actress who can replace Ms. Holmes
in the big-budget picture, for which the salary range likely would
have been $1 million to$2 million, say these people, compared to the
roughly $1 million she earned for "Batman Begins."

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