An eye-popping price tag in Connecticut is a new test of the ultra-high-end property market

Named Copper Beech Farm, the Greenwich, Conn. estate sits on 50½ acres and includes a 12-bedroom Victorian, French-renaissance mansion, 4,000 feet of water frontage on Long Island Sound and two offshore islands. Natalie Keyssar for The Wall Street Journal

The 50½-acre property includes a 12-bedroom Victorian, French-renaissance mansion, 4,000 feet of water frontage on Long Island Sound and two offshore islands.

A number of U.S. properties that marketed themselves with price tags of $100 million or more have wound up selling for less—or not selling at all. While record price tags can drum up attention for the property—a vanity price is a great way to get your 15 minutes of fame, notes New York real-estate agent Donna Olshan —they can also lead to multiple and very public price reductions.

ENLARGE

A 50-acre waterfront estate in Greenwich, Conn. is hitting the market. At $190 million, it is believed to be the highest price to date for a U.S. listing. Does it have a shot at getting that price? Photo: Natalie Keyssar for The Wall Street Journal.

In 2009, Candy Spelling put her Los Angeles 123-room mansion on the market for $150 million, garnering keen attention. British socialite Petra Ecclestone bought it for $85 million, or 57% of the asking price, in July 2011. The Beverly Hills, Calif. compound of William Randolph Hearst and Marion Davies was listed for $165 million in July 2007. It’s still on the market, now for $115 million, with less land and fewer structures.

Some of the biggest recent sales have involved properties that were never publicly listed at all. Private-equity chief Tully Friedman’s nearly 9,000-square-foot home in Woodside, Calif. in Silicon Valley, wasn’t publicly on the market when it sold to SV Projects LLC in November 2012 for $117.5 million, the most expensive recorded home sale in the U.S.

Appraisers say unique and luxurious properties can be extremely difficult to value accurately. Typically, real-estate agents use comparable recent sales and appraisals to help determine what the market will bear. But in the top tier of the luxury market there are few, if any, comparable listings.

When it gets that high in price, [comparable listings] no longer make sense, says Mayi de la Vega, an estate agent in Miami who is getting ready to list a property for more than $100 million.

While there is no national comprehensive database of listing prices, multiple real-estate brokers around the country didn’t know of a listing as pricey as the Greenwich property. An estate in Dallas for $135 million is believed to be the second-highest-priced home on the market.

The Greenwich property’s listing agent, David Ogilvy, of David Ogilvy & Associates, an exclusive affiliate of Christie’s International Real Estate, says it’s difficult to know what something so rare is worth. It’s one of these things where you cannot look and say ‘It’s worth X,’ because there’s nothing like it, he says, adding that the last 50-acre waterfront estate in Greenwich was sold and subdivided in 1954.

Called Copper Beech Farm after the large copper beech trees on the property, the Greenwich estate once belonged to the Lauder Greenway family—Harriet Lauder Greenway’s father helped Andrew Carnegie start what would become U.S. Steel —and dates back to the 1890s, says Mr. Ogilvy. The current owner is timber tycoon John Rudey, according to public records. Mr. Rudey, who knew the Lauder Greenway family, bought the property quietly 31 years ago, Mr. Ogilvy says, adding that the owner is selling because his children have grown.

Located five minutes off the main I-95 highway, the property is next to Mead Point, a private association with some of Greenwich’s most prominent estates. Wild turkeys regularly visit the estate (the gatekeeper likes to feed them) and a 1,800-foot-long driveway meanders up to the main house, which has 15,000 square feet of living space, along with an additional 7,000 square feet of basement and attic space. Built in 1896, the main home has a three-story, wood-paneled entry, a dining room with an elaborate ceiling and a solarium.

While in good condition, the interior needs upgrading; Mr. Rudey, for example, had plans drawn up to design a kitchen off the dining room, as the main kitchen is in the basement, which was part of the staff quarters. There are old speaking tubes from pre-electricity days and sleeping porches, which were once used in warmer months before air conditioning was the norm.

Much of the property’s value is in the land, which is owned in two parcels—a 20-acre property and a 30-acre property. The latter property includes a grass tennis court, formal gardens that a former horticulturalist of the New York Botanical Gardens maintains, a carriage house, two greenhouses, a 75-foot-long heated pool with a hot tub, a pool house and an apple orchard.

Mr. Ogilvy says there have been subdivision studies done on the property. Part of the listing price was based on appraisals done by the current owner that valued the combined property at well over $200 million based on its highest and best use, which would suggest splitting up the estate. (Such changes would have to be approved by a zoning board.) What makes this property so special, Mr. Ogilvy says, is that it’s still at its original size.

Assessments made by the Greenwich assessor’s office represent 70% of the market value, a spokesman says, with homes on the water being the most valuable. Land typically accounts for 60% of the valuation. The assessed value of both properties making up Copper Beech Farm is $14.94 million. The most expensive current assessment in Greenwich is $30.6 million for a waterfront 9.2-acre property.

Greenwich, a town filled with old-money estates, is no stranger to grand listings. In April 2008, hotel mogul Leona Helmsley’s mansion hit the market for $125 million. It sold for $35 million, at a 72% discount, in October 2010. Less than a year later, the estate went back on the market for $42.9 million and has since been withdrawn. The most expensive sale in Greenwich in the past five years was a 20,777-square-foot waterfront mansion that sold in less than a year for $39.5 million, or 93% of the $42.5 million list price.

Pricing a home far above its neighbors can be a risky bet. In July 2012, Steven Klar, owner of a residential-real-estate development firm, put his 8,000-square-foot penthouse on the 73rd to 75th floors in Manhattan’s CitySpire building on the market for $100 million. Though nothing in the building has sold for more than $3.4 million in the past five years, Mr. Klar says his property shouldn’t be judged by the value of lower floors. He also says he spoke with various brokers who told him they could see a list price of $75 million, $80 million or $90 million.

I said, ‘If we go to $90 million, why not go to $100 [million]?’ says Mr. Klar, who adds that he put the penthouse on the market because he felt the terraces posed a potential danger to his 5½-year-old son. We need the impact. In January, Mr. Klar let the listing expire, but he is still shopping it around through his firm.

Corrections & Amplifications

John Rudey bought Copper Beech Farm 31 years ago. An earlier version of this article incorrectly said he bought it 28 years ago.