Girl-next-door Katie Holmes could make a mint charging by the hour – but pit-bull-in-lipstick Alaska Gov. Sarah Palin should keep her day job.

So says Manhattan madam Kristin Davis, dishing on how celebrities would fare in the world’s oldest profession.

In an interview with Steppin’ Out, the Wicked Models boss arrested after the Eliot Spitzer scandal rated A-listers on how much they could earn as ladies of the night.

“Katie would be very popular because she has that All-American college girl look,” Davis said of Tom Cruise’s wife.

“I could probably get $2,500 an hour for Katie. Maybe even $3,000.”

Angelina Jolie would also be a crowd pleaser. “She would be my top girl. I call it my ‘Number One,'” Davis said during an interview at the Thompson Hotel.

“I would put her at $2,000 an hour. But you couldn’t get her unless you booked her for four hours.”

Davis thinks Britney Spears could command $2,000 an hour, too, now that she has cleaned up her act. During her shaved-head period, she would have earned half that, she said.

Davis, who served three months in jail, is about to publish a book, “The Real Sex in the City: True Tales of the Manhattan Madam.”

She claims it will contain the names of powerful politicians, Wall Street bigwigs, celebrities, doctors and lawyers who patronized her call-girl ring.

Some of her prostitutes earned up to $1,600 an hour, but Davis says not everyone can command those prices.

Take former vice presidential candidate Palin.

“I wouldn’t have any market for her,” she said. “She’s cute, but not for my kind of clients … She could work for a cheaper agency – maybe a $300-an-hour type agency.”

In Davis’ opinion, Britney Spears, Paris Hilton and Melania Trump also all would fare well in the oldest profession, fetching upward of $2,000 an hour. Most Playboy Playmates, on the other hand, are too “fake looking” and their “boobs are too big” to draw top dollar from her usual clientele.