An upper-crust Long Island housewife accused of hiring a hit man to off her hubby lamented she could only afford to maim him — but then was thrilled to learn she could whack him at a bargain-basement price of just $20,000, authorities said yesterday.

That’s the stone-cold, cost-calculating mentality of sick soccer mom Susan Williams, 43, who allegedly hired an undercover cop this week to whack her husband of 21 years. She was held yesterday on $1 million bail.

The twisted plot didn’t surprise her long-suffering spouse, Peter Williams.

His lawyer said the woman “tortured” the poor man with sick lies during their divorce in a grab for their million-dollar Garden City home and other cushy assets.

She even allegedly turned their four kids — ages 11 to 19 — against him.

“I can’t believe it took her this long” to try to kill Peter, said his divorce lawyer, Nancy Dreeben.

“She’s a desperate woman, and she will just do whatever she needs to do to get what she wants. She’s a narcissist.”

Dreeben said Susan admitted she cheated on her husband during their marriage — even bedding the real-estate lawyer for whom she worked before he fired her.

Susan stole marital assets and then, after filing for divorce in 2008, falsely accused Peter — a 46-year-old fence-company owner — of physical violence against their kids and of forcing her to have deviate sex, Dreeben said.

Those claims were never substantiated and Susan a year later even willingly agreed to allow Peter visitation rights, the lawyer noted.

Peter Williams, 46, a Baldwin resident who is now working to get custody of his kids, said, “I am thankful that the person that my wife sought to help in hiring a hit man had the decency to contact the appropriate authorities — otherwise I would probably be dead.”

But yesterday, Susan’s lawyer painted a different picture, accusing the husband of being abusive and a deadbeat dad.

“There’s a long history of problems, physical and sexual,” in the marriage, attorney Stanley Kopilow said. “He’s not a nice guy.”

Susan’s dad, Brendan Galligan, sobbed outside his Long Island home while defending his daughter.

“She had no money, and he wasn’t paying for anything. She was having a very hard time,” Galligan said.

“We tried to help her as best we could as parents, but now this happens,” he said. “It’s totally devastated my wife and me.”

Dreeben admits Peter has failed to pay court-ordered monthly child support of $11,000 because he can’t afford it.

She also said that sky-high amount was set by a judge after Susan lied about the couple’s finances.

Susan was busted Thursday after authorities secretly recorded her negotiating with the “hit man” — actually an undercover cop.

Susan had previously asked an unidentified man for help in arranging the attack on her husband, Nassau County DA Kathleen Rice said. That man contacted the DA.

“Initially it was, ‘I want him hurt,’ ” Rice said. “Then it became, ‘I want him gone.’

“She didn’t think she could afford [a murder]. She didn’t realize it was so cheap. When the $20,000 amount was thrown out” by the purported hit man, “she then made it clear what she wanted him to do,” the DA said.

After learning the price, Susan allegedly forked over a $500 down payment as well as her husband’s photo and personal information, but no more money changed hands.

Additional reporting by Selim Algar and Murray Weiss

kieran.crowley@nypost.com

