Deeds filed in city records this month show that the investor Lily Lee Lee Wong paid $12.1 million for the 15-room, 115-year-old townhouse at 21 East 84th Street—on the corner of Madison Avenue, where the house has a petite commercial space. Her contract closed in June, and by the end of July she had listed the place for $24.5 million, more than twice what she paid.

That price boost is even more steroidal than William J.B. Brady’s new $12 million tag for his Village duplex penthouse, which he paid $6.95 million for barely five months ago.

Ms. Wong’s seller is the philanthropist Maryam Ansary, ex-wife of Hushang Ansary—a massive Bush fund-raiser and the former Iranian ambassador to the United States.

Why is Ms. Wong’s price so high? “I don’t have that answer,” said her listing broker Alice Caceres, a sales associate at Bellmarc Realty. Ms. Caceres said her client was redoing the kitchen and the bedrooms’ hardwood floors. “Let me see, what else? I think that’s it.”

Ms. Caceres, who said she had never listed a property for more than $2 million, would not discuss Ms. Wong.

But this isn’t the first time a woman has tried to flip this terra-cotta townhouse for a massive profit. City records show that Ms. Ansary bought it in October 2003 for $5.5 million, and a month later the house was on the market for $20 million. She cycled through three brokerages, and her price eventually went down to $15.5 million.

Prudential Douglas Elliman’s Atoussa Haskin and Dolly Lenz were the most recent listing brokers for Ms. Ansary. “I don’t quite get what she’s doing here,” Ms. Lenz, probably the most formidable agent in New York, said about Ms. Wong. “But obviously at $25 million she’s not going to do it—in my opinion.”

When asked about Ms. Wong’s Bellmarc associate agent, Ms. Lenz said: “I had never heard of the broker even!”

Though the house spent four years on the market before this summer’s sale, the place was designed by Grant’s Tomb architect John Duncan, and it has original stained lead glass windows, six wood-burning fireplaces, and more than a half-dozen crystal chandeliers. Plus, the store that sits in the Madison Avenue side of the townhouse’s first floor, Artbag, reportedly brings in about $280,000 per year in rent.

On the other hand, there’s no backyard, and 84th Street is so busy that, as Ms. Lenz deadpanned, “You can’t have kids playing in front because they’ll get hit by a car.”