Manhattan apartment prices jumped to a record in the second quarter, pushed up by competition for a limited number of properties and strength in the luxury market. Resale apartments and units in new developments each set their own price records amid interest from both investors and buyers who intend to live in the homes. “Demand is being driven by a vibrant local economy and rising employment, and supply is relatively inelastic,” Jonathan Miller, president of New York-based Miller Samuel and a Bloomberg View contributor, said in an interview.