Because a room with a view has always been preferable to one without, the price of air in New York City is becoming more expensive. Yes, the air is for sale, but not on sale.

And not the dodgy urban air the city’s eight million inhabitants breathe as they scurry around the boulevards, but the rarefied and fast-disappearing air overhead where condominium towers do not fear to tread, and rooms with sunlit windows can make the lucrative difference between a legal three-bedroom residence and a mere two-bedroom with a den/office.

With Manhattan’s skyscraper-proof bedrock in finite supply and the city’s fixation on housing and envelope-pushing office buildings on the upswing — and also the impetus behind the proposed rezoning of 70 blocks around Grand Central Terminal called Midtown East — the sky is not only the limit, it’s the solution. Ubiquitous developers-about-town like Gary Barnett, Harry B. Macklowe and the Zeckendorf brothers are all not-so-secret members of the air appreciation society.

“When I tell people outside of New York that I’m buying air from other building owners, they look at me as if I’ve lost my mind,” said Kenneth S. Horn, the president of Alchemy Properties. His 18-story Isis Condominium at 303 East 77th Street acquired air rights from two adjacent tenements; it cantilevers eight feet above the roofs of both of them beginning at the sixth floor. The payoff for this complex and expensive undertaking is 360-degree views, more spacious apartments, abundant light and higher resale value.