Left: Duplex penthouse on Madison Square Park in New York's Flatiron district. Listed at $25 million.

Where the well-heeled Cohen dismisses any notions of brokerly competition, Melanie Lazenby—the leggy, Louboutined daughter of the actor and onetime James Bond George Lazenby—describes a high-stakes arena rife with rivalry, reconnaissance, and retribution. "It's like a little mafia," Lazenby, 39, says over lunch at the posh Italian eatery SD26 in New York's Flatiron district. "There's a spirit in this business of keeping your enemies close." The co-brokering system, in which buyer and seller typically bring their own representatives to the table, compels all the alphas in town to play well with others—at least initially. "I can be as nice as I want to be, but cross me and it's not pretty," she says. "We'll feed each other and help each other, but we'll also fucking kill each other. If you try to poach one of my clients, I'll become your worst nightmare."

Lazenby holds the distinction (which she shares with her partner, Dina Lewis) of selling the most expensive condo in downtown Manhattan twice: The first time was in 2010, when she sold the West Village penthouse of the Houston Rockets owner and billionaire financier Leslie Alexander for $31.5 million; the second time was in 2012, when she bought a $42 million Gramercy Park penthouse for . . . Leslie Alexander. At least some of the credit for her success, Lazenby says, belongs to her father: "One time, some guys tried to carjack us on the Sunset Strip," she recalls, "and my dad just laughed hysterically and took off through the red light. He told me, 'You need balls to pull the trigger, and I didn't see one set of balls.' For my job, that was the best training in the world."

Extraordinary nerve and pluck have become as much a part of the luxury deal as glassed-in wine walls and marble bathrooms with heated floors. Buyers, sellers, and brokers alike are equally versed in audacity. "On one sale," says Drew Fenton, 30, a Los Angeles–based broker currently listing a $57.5 million Malibu compound designed by Frank Gehry, "the buyers wanted the seller's dog. I thought it was a joke, but it wasn't. We had to find them an equivalent." So if an AKC-certified pooch completes the picture for the buyer, you find one.

It is, after all, about selling a dream. Branden Williams, who grew up in Los Angeles peddling animal skins and rugs on the side of the road, says he once sold a $27 million home to a buyer with a $6 million budget. Prior to that, he parlayed a meeting with a billionaire developer into a series of plum listings in the Hollywood Hills. Williams immediately found fault with the older Realtors who'd been showing the properties. "At around seven o'clock," he gripes, "these ladies would go home and turn off their phones. These are all panty-dropper, single-guy homes. They look good in the daytime. But at night they look incredible."

Left: Hollywood Hills estate with a 9,200-square-foot six-bedroom home and a private grotto. Listed at $19.8 million.