“Traditionally, condominiums were not of the caliber they are today,” Mr. Steinberg said. “However, the super-luxe buildings being developed today are condos that allow for this very high-end investor-landlord.”

This surge of development has also resulted in what Mr. Miller described as an “oversupply” of superbly finished, highly amenitized ultraluxury rentals that “force developers to pull out all the stops to compete.”

Mr. Rothstein’s apartment, for instance, has a private-elevator entrance, 14-foot barrel-vaulted ceilings and a wall of eight-foot windows that runs the entire length of the loft, with a clock-tower window so massive you can see it from nearly three blocks away. The building also has a state-of-the-art gym with sauna and rooftop access to a park-inspired common area that is currently under construction.

Farther uptown, a $60,000-a-month, five-bedroom, eight-bathroom apartment at 35 East 63rd Street currently on the market offers 6,312 square feet of space on the top two floors of a neo-Grec townhouse and more than 4,000 square feet of private outdoor space, including four terraces and a rooftop deck of helicopter-landing proportions. The seven-unit converted mansion also comes with a 24-hour doorman.

Over at the $100,000-a-month penthouse atop 988 Fifth Avenue, renters get more than a coveted address. Along with floor-to-ceiling views of Central Park and two landscaped terraces, the two-level home has daily housekeeping service, an on-staff gardener and a weekly supply of fresh flowers delivered and arranged by a prominent local florist. “In many ways, you’re buying into a lifestyle experience without having to commit to anything,” said Leighton Candler, a Corcoran Group agent who represents the penthouse.

As unlikely as it seems, renting such a lifestyle at this dizzying end of the market could offer cost savings. “Short-term rentals can wind up being a lot more economical than buying or renting at a hotel,” Mr. Steinberg said.