Metro

The $ky’s the limit

Only in New York can you sell air for $500 a square foot.

That’s how much the rarified sky around the High Line is now worth, a record price that is $125 more per foot than the land beneath it.

When developer Sherwood Equities plunked down $7.3 million last April to purchase a graffiti-covered, half-built shell of a building at 508 W. 20th St., the property’s close proximity to the heavily-trafficked elevated park seemed like its main selling point.

But the developer realized the real gold mine wasn’t in throwing up a five-story condo on the 4,000-square-foot lot — but in selling the undeveloped air above it.

Sherwood Equities now stands to pocket a cool $10 million just by selling off 20,000 square feet — equal to five stories of empty space — of air rights.

Even by New York City standards, “it’s an extraordinary amount of money,” said real-estate appraiser Robert Von Ancken.

Air rights in Manhattan are typically worth half the value of the land beneath them, he said. But a limited supply and growing demand to build higher in Chelsea has driven up the price of High Line air rights.

“About two-thirds of the air rights are in contract,” said Ryan Nelson, 31, who oversees development at Sherwood. He said he is fielding multiple hungry offers for the last 8,000 square feet.

And he will still use the lot to build “a one-story restaurant or gallery that will have a roof at the High Line.”

Explaining the millions he’s raking in by selling air, Nelson said, “There’s a very [small] supply of something that, in essence, allows you to increase the best part of your building — the height and the views.”

Typically, air rights can be sold only to an adjacent building. But in 2005, the city cut a break around the former rail trestle. Property owners in the corridor abutting the park between West 18th Street and West 30th Street could sell air rights to sites throughout West Chelsea.

The purpose was twofold: to give a boost in value to property owners who opposed construction of the park, and to ensure that tall buildings didn’t block air and light from flooding the nascent green space.

About 276,940 square feet of air rights along the High Line have been sold since 2005, according to the Department of City Planning.

But now the limited and dwindling supply of air rights — about 60,000 square feet of transferrable rights remain — is making High Line millionaires out of the last lucky developers hawking air.

“We’re taking advantage of High Line air rights,” said Nelson.