Is New York City’s famed Fifth Avenue losing its luster? It's perhaps the most luxurious street in the world. Louis Vuitton, Tiffany, Valentino and Harry Winston all have stores there. These days it's dotted with vacancy after vacancy, according to real estate consultant Jonathan Miller. "This phenomenon nationwide has been called the retail apocalypse," he said. Part of the problem may be Trump Tower, which has had a negative impact on foot traffic, but the main culprit is the rent.