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Cyndi Lauper (search) may be a pop-star who's sold millions of albums, but that doesn't mean she wants to pay much more than $500 for her apartment on Manhattan's Upper West Side.

Lauper, 51, and her husband David Thornton (search), an actor who's appeared in numerous movies, including "A Civil Action" and 2002's "Swept Away," with Madonna, are suing the owners of their luxury apartment building. Lauper and Thornton claim they were cheated out of thousands of dollars in rent in a scheme to end rent stabilization for their residence.

Lawyers for the two sides are scheduled to appear before the state's highest court, the Court of Appeals, on June 7. That's just before Lauper, known for her 1980s hits "Girls Just Want to Have Fun," "Time After Time" and "I Drove All Night," starts a short tour to support her recently released live album.

In 1992, 390 West End Associates entered into a lease with Shlomo Baron for an apartment in its building in Manhattan. While the prior tenant had paid just $508 a month for the rent stabilized apartment, Baron agreed to pay $2,400 a month under an agreement he would not use the dwelling as his primary residence.

Baron then sublet the apartment to Lauper and her husband for $3,250 a month, according to court documents.

Six months later, a state Supreme Court judge ruled the apartment was exempt from the rent stabilization law because Baron wasn't using it as his primary residence.

In 1996, the Thorntons sued Baron, seeking to recover what they paid in excess of the legal stabilized rent plus damages. In 1999, 390 West End moved to vacate the judgment it won in getting the apartment exempted from rent stabilization on the grounds its agreement with Baron was illegal. That motion, which ended the lease with Baron, was granted in 2000.

Subsequently, the Thorntons sued 390 West End, seeking to get their rent reduced to the stabilized price of $508 a month.

Supreme Court ruled in favor of the Thorntons except for the manner of determining rent. The court determined that the four-year limitation period adopted in the Rent Regulation Reform Act of 1997 (search) precluded it from considering the rent history before 1996, four years before the Thorntons' suit against the building owner.

However, the court rejected 390 West End's argument that rent should be set at the $2,400 a month Baron agreed to pay. Instead, the court used a default formula adopted by the Division of Housing and Community Renewal (search) to determine rent should be set at $989 a month.

The Appellate Division of state Supreme Court upheld that ruling.

Magda Cruz, an attorney representing 390 West End Associates, declined to comment on the case before speaking with her client.

Darryl Vernon, the attorney representing the Thorntons, did not return a call for comment.