Some boutique buildings still offer amenities, too. For example, at The Benson on the Upper East Side, Ms. Lambert said the 15 residences share a library, an art room, a movie theater, a half-size basketball court, and multiple outdoor spaces. Prices start at $12.8 million. The 13 residences at 555 West End Ave. are prized for their architectural quality, with 12-foot-high ceilings in every room, but the building also has a doorman, a lounge, and a private fitness center, Ms. Lambert said. Prices at 555 West End Ave. range from $8.4 million to $22.5 million.