The skin-tight pants and black leather jacket Olivia Newton-John wore in 1978’s “Grease” have sold for $405,000 at auction — nearly twice what they were expected to fetch.

An unnamed buyer on Saturday shelled out $243,200 for the jacket and $162,500 for the pants made famous by the four-time Grammy Award-winning actress in the hit film’s “You’re the One that I Want,” finale.

Martin Nolan, executive director of Julien’s Auctions, which hosted the event, told The Post last week he expected the items to sell for $260,000 — just over what the buyer paid for Newton-John’s leather jacket alone.

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“If you ask Olivia, she thinks it’ll go for a million dollars,” Nolan said Wednesday of the outfit. “It’s so iconic, I wouldn’t be surprised.”

“She wore them a couple weeks ago — they still fit,” he added.

Olivia Newton-John and John Travolta appear in "Grease." Newton-John's iconic tight pants and top from her "Bad Sandy" transformation went on auction for big bucks. (Getty)

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The slinky pants actually predate the film by nearly two decades. In an interview with Reuters last week, Newton-John said the zipper on the pants, made in the 1950s, was broken and she had to be sewn into them for the film.

The sexy outfit was among 500 items the Australia-born actress, now 71, auctioned to raise funds for her breast cancer charity. Newton-John is currently in her third battle with the disease.

Also up for auction was Newton-John’s custom Pink Ladies jacket embroidered with “Sandy,” the name of her character in the movie, a signed “Grease” script, and her white cowboy boots from the 1980 flick “Xanadu.”

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“I’ve realized over the years, especially when you go through stuff, that stuff isn’t what’s important,” she told Reuters of her decision to auction off the items.

This article originally appeared on Page Six.