The shimmering limestone tower at 15 Central Park West, where apartments routinely trade for upward of $20 million, has become symbolic of the most luxurious upper reaches of New York’s real estate market. Its architect, Robert A. M. Stern, is the dean of the Yale School of Architecture. The views stretch out over the expanse of Central Park. And earlier this year, a single penthouse sold for $88 million.

Yet despite its sublime finishes, refined pedigree and nosebleed prices, the residential portion of that Manhattan building is officially valued by the city, for tax purposes, at only $332 per square foot. In reality, the average price per square foot for apartments sold there over the past 18 months has been $7,813, according to the Miller Samuel appraisal firm.

That kind of disparity is true for many of the stratospherically expensive apartments in the city. As a result, their owners pay far less in property taxes, relative to the value of the apartments, than most New York apartment owners pay. So despite a boom in the upper echelons of the real estate market — 125 apartments have sold for at least $20 million in the last five years, and developers are churning out more every year — the city is unable to truly cash in.

The effect ripples down from there. “If a certain kind of property is systematically undervalued, another kind of property has to pick up the slack,” said Andrew Hayashi, a property tax expert at the Furman Center for Real Estate and Urban Policy at New York University.