Weill Penthouse

Miller traced the beginning of the latest boom to last November, when developer William Lie Zeckendorf sold his penthouse at 15 Central Park West for $40 million. Also that month, the penthouse at Superior Ink Condominiums and Townhouses in the West Village sold for $31.5 million, a record price for a downtown Manhattan condo, Miller said.

Another record could be broken if former Citigroup Inc. Chairman Sanford Weill sells his penthouse at 15 Central Park West for anything close to the $88 million asking price. Weill put his 6,744-square foot (627-square-meter), full-floor condo on the market on Nov. 11. The most expensive Manhattan residential transaction so far is a $53 million townhouse deal in 2006, Miller said.

Data from StreetEasy show 12 completed transactions for $20 million and above in the three months ended Sept. 30, the most since the same period of 2008, when there were 20.

'Herd-Like Mentality'

A "herd-like mentality" has spurred luxury buyers in the past several quarters, said Noah Rosenblatt, founder of UrbanDigs.com, a real estate analytics and consulting company in New York.

"When they start to see apartments go into contract again and again, they start to think their options are being limited," he said. "They're more willing to pull the trigger on a deal."

Data compiled by UrbanDigs show demand for apartments priced at $5 million and above began to rise in February. Pending sales -- the number of properties that moved from an active listing to a signed contract -- jumped from 70 in February to 152 in late April. That was the biggest resurgence in that price range since 2008, Rosenblatt said.

A significant number of those deals probably were completed in the three months through September and were reflected in third-quarter sales data, according to Rosenblatt.

Slowdown Looms

Reports for the fourth quarter probably will show a drop- off because of a seasonal slowdown and economic turmoil that may have hurt contract signings, he said. On Nov. 14, UrbanDigs data showed 104 apartments under contract for at least $5 million, down from a post-recession peak of 156 at the end of July.