SThe Palazzo Chupi penthouse, part of artist Julian Schnabel's giant pink building on West 11th Street, has cut its asking price again, from $29 mil to to $24 mil. (It dropped to $29.5 mil from $32 mil last May.) The story isn't just that an artist can't sell a big pink mansion in the West Village, though. The slashing of the price tag on Palazzo Chupi represents not just a reverse for the building's colorful creator; it marks the end of an era for New York artists.Palazzo was the most recent and ambitious artist-designed real estate project, so it makes sense that it'll be the one to fall first, with its inability to sell and hubristic asking price. For 50 years artists have supplemented unreliable income from their work with real-estate gains. Now New York is likely to experience the first significant decline in real-estate prices in decades. Artists may or may not find the city's neighborhoods more affordable; but Schnabel and others can no longer expect to share in the appreciation of neighborhoods they make hip. It's fair to say that there won't be large projects like this in the future, and that Schnabel will be regarded as the peak of the heady days of the artist-developer.