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Details are crucial: It's not enough for a wall to be fine marble; it has to be book-matched, so the lines flow naturally. "It's expensive and time-consuming," Murphy said. Onyx and mother of pearl are in vogue.

The bigger the better. One custom house Coastal is building in Hillsboro Beach, Fla., is set to be 60,000 square feet. That's about the size of 50 two-bedroom apartments. "A beautiful big home," Murphy said.

A huge issue: South Florida -- especially Miami -- is running out of prime oceanfront and bayfront sites. "Land has been scarce. A majority of the projects we're touching are all knock-downs. Or it's been knocked down by the time we get there," Murphy said. "You're seeing more people buying not one lot, but one, two, three."

Coldwell Banker luxury super broker Jill Eber -- who works with Jill Hertzberg as The Jills in marketing many of South Florida's most exclusive homes -- said tear-downs are increasingly common.

"We just closed at the end of the year on a property at the tip of Sunset Island for $20 million," said Eber, whose team had the listing for the record $47 million Indian Creek sale and closed on some $480 million in residential deals in 2012. "Somebody bought it for $20 million and is tearing it down. It's only about 46,000 square feet (of lot), but it's got 200 feet on the open bay looking directly downtown."

"At the highest end, a luxury home is of the moment, right now," Hertzberg said. "It's current, with all the bells and whistles and amenities."

Many buyers at the top of the Miami market are snubbing the long-popular Mediterranean-style architecture of barrel-tiled roofs and stucco walls in favor of sleek, contemporary, mostly glass houses.

"People are asking more and more for contemporary, clean lines," said Audrey Ross, senior vice president of Esslinger-Wooten-Maxwell and a top-selling luxury Realtor who has sold many of Miami's prime estates several times.

Wayne M. Boich Jr., the 37-year-old CEO of the Boich Group of Companies, a Columbus, Ohio-based coal business, bought three adjoining bayfront properties in Miami Beach for $17.7 million last July and knocked down the homes to make way for a sleek, contemporary home bigger than all three.

Boich, known on the party circuit for throwing lavish gatherings, sold his penthouse on Miami's South Beach for $21 million last year.

He and fiancee Cynthia Marin, who plan to marry in March, are building a 17,975-square-foot crystalline glass palace designed in a series of horizontal rectangles perched on a wide swath of Biscayne Bay.

"Finding the right lot took a significant amount of time. We were really happy to gather this together. It's been really exciting," said Boich, who hopes to move in early next year. "It's a modern feel, a sleek feel."

Miami architect Kobi Karp, who also is doing some of Miami's most upscale condominiums, said effort was focused on taking advantage of the spectacular view of Miami and downtown. The building, which he describes as "floating rectangles" will have "huge verandas and terraces to create shade" on the mostly glass facade, he said.

Karp said the project is all about superlatives: "Anything that's been done before in Miami we had to meet, greet and beat it."

Keeping up with the Joneses requires as much. A few blocks south of Boich is the jaw-dropping home of New York Yankees slugger Alex Rodriguez. A-Rod recently had the spacious contemporary mansion listed with One Sotheby's International Realty for $38 million but took it off the market and rented it out.

To the north is a lavish home formerly owned by Jennifer Lopez, now owned by health care executive Mark Gainor, who has listed it for sale for $40 million.

Boich took some heat from locals for his extravagant plans. While two of the houses he bulldozed were in poor condition, the third, built in 1964 by architect J. Arango, was a Miami Modern-style structure that some thought should be preserved.

Some of the more fanatical fans of the Miami Heat, which clinched the NBA championship in 2012, might argue a former home of Pat Riley deserves to be preserved and turned into some sort of monument.

Riley, who bought the home in 1996 for $6.3 million, declined to comment. "Unfortunately, Pat is not interested in being quoted for your story," Heat spokesman Tim Donovan said in an email.

The individual behind the corporation that bought the home has not been identified.

As for Boich, who says he played in the U.S. Tennis Association Junior International Championship as a teenager, he wants a top-notch tennis court on the northwest side of his property next to a swank glass-walled gym and spa overlooking the bay and downtown Miami. "We're very interested in sports," said Boich, who plans to live in the place and "raise a family."

For many of the world's one-percenters, however, a Miami mansion is a third, fourth or fifth home. Some collect homes like others collect cars or art -- or, at more plebeian levels, stamps or coins.

"It's a discretionary purchase, almost 100 percent of the time," said Ross, of Esslinger-Wooten-Maxwell. "Generally speaking, my business in the ultra high-end tracks the stock market one-to-one. I can watch the ticker and know if I'm going to be busy or not. Right now, the high end is flying."