An individual buyer — a Delaware limited liability company whose owner could not yet be determined — paid billionaire Ken Griffin $19 million Tuesday for the top two floors of the 38-story luxury Near North Side building at 9 W. Walton Street. That combined purchase represents the highest price anyone has paid this year for a Chicago-area residence, and it meant that Griffin lost more than $15.1 million on the two condominiums and that he now has lost almost $22 million on Chicago condos he has sold. Public records reviewed by the Tribune show that Chicago Skyline Properties LLC, a Delaware limited liability company that was formed last year, was the buyer of the 15,000-square-foot unbuilt space at 9 W.