Most Expensive Residential Development Ever Constructed

One57, the $1.4 billion project, across from Carnegie Hall, already is about 50 floors above ground. When completed in 2013, the 90-floor property will tower over Central Park at 1,004 feet. Penthouses are listed at $98.5 million each, with most apartments listed between $21 to $45 million.

Mr. Barnett and his partners are among a small band of developers borrowing heavily and rolling the dice on a highly select clientele: the global elite who float above the economic malaise. While a hallmark of the economic downturn has been the collapse of the housing market, the extreme top of residential market in New York has been resilient.

Mr. Barnett says the number of billionaire and multimillionaire investors in the world has never been greater. In addition to Russians and Western Europeans, he says, "you're seeing Latin Americans in a big way. You're seeing Chinese in a big way. You're seeing the return of the Middle Eastern buyer." Thanks to this demand, the ultra luxury market in select cities is looking healthier than practically any other corner of the housing market.

In March, Russian pop-music composer Igor Krutoy paid the highest price ever for a New York condo, shelling out $48 million for 6,000 square feet of space in the Plaza hotel with a sweeping view of Central Park. Through November, buyers in Manhattan signed 529 contracts for apartments priced at $4 million or more, the fastest pace since 2007, according to the Olshan Luxury Report, which tracks high-end residential sales.

The rise of an affluent class in the developing world is driving much of the action. China has 5,400 individuals who are worth at least $50 million, which ranks it above every country but the U.S., according to the Global Wealth Report from Credit Suisse. Russia, Brazil and India each have more than 1,500 of these so-called ultrahigh-net-worth individuals.

Besides offering status, luxury condos are viewed as a way to preserve capital when financial markets offer poor returns or when there is concern, as in the Middle East, about government stability. In most downturns, luxury property holds its value better than the market as a whole.

  Still, Mr. Barnett's wager has plenty of risk. A dive by the U.S. economy or a deepening of the European debt crisis would crush financial markets, reducing the ranks of the wealthy. Wall Street firms already have begun eliminating thousands of positions.

Other New York condo projects that targeted the upper crust have cratered because of poor timing. In the early 1990s, developer Bruce Eichner turned over to creditors a soaring 73-story tower that was packed with amenities and also aimed squarely at international buyers. It was located just one block away from Mr. Barnett's project. Extell and its partners could get stuck with a shimmering building full of unsold condos and a limited income stream to pay off massive debt.

Most of that pain would be borne by the Abu Dhabi funds, which have put in about $650 million of the project's equity. Extell has put up $50 million, though it could get a bigger piece of the profits if sales go well. The Abu Dhabi partners also have guaranteed to buy back the loan if sales targets aren't reached.

Extell isn't the only condo developer courting these buyers. CIM Group and developer Harry Macklowe are building a 1,420-foot condominium at 440 Park Avenue, which will be the tallest residential tower in the western hemisphere.

Mr. Barnett says within a week of opening his salesroom last month, One57 had two signed contracts for $45 million each.