Speculators are tapping the demand, snapping up the best lots, bulldozing whatever is on them and building not only domiciles but also West Coast “lifestyles.” The particulars can seem a little puzzling to the uninitiated. The very busy Mr. Niami (he also built the Winklevoss twins’ perch above the Sunset Strip) constructed a 30,000-square-foot Mediterranean-style house in Holmby Hills that locals have called the Fendi Casa because it was filled with furniture and accessories from the Italian fashion house.

The residence also offered indoor and outdoor pools, commissioned artwork by the graffiti artist Retna, and an operating room in the basement. “It’s not like it’s set up to take out your gallbladder,” said Mark David, a real estate columnist for Variety, who has toured the house. “It’s for cosmetic procedures — fillers, dermabrasion, that kind of thing.” The house sold, with all its furnishings, to an unidentified Saudi buyer for $44 million.

A relatively humble 23,000-square-foot modern spec house currently on the market in Beverly Hills’s Trousdale Estates neighborhood has an infinity pool with iPad-controlled fountains and a subterranean lounge with floor-to-ceiling candy dispensers on one wall and mounted tequila bottles and machine guns on another. The lounge opens onto a 16-vehicle garage with a Bugatti Veyron revolving on a car turntable, just like at the dealer’s. According to TMZ, Beyoncé and Jay Z looked at the property twice. The asking price is $85 million, not including the Bugatti.

Mr. Rosen is hardly alone in his objection to the disruptions created by these pumped-up projects. Another house in Bel Air developed by Mr. Hadid — a Palestinian émigré with a flowing gray mane and a burnt sienna tan — is the scourge of nearby residents. The 30,000-square-foot house, a modern, circular colossus that has been nicknamed the Starship Enterprise by angry neighbors, who include Leonard Nimoy, looms 67 feet above grade (the height limit in Los Angeles is 36 feet). “He’s violated just about every regulation that applies,” said Joseph Horacek, an entertainment lawyer who lives directly below the home and has filed numerous appeals against the project. Last month, the city revoked the developer’s permits.