In December, Christie’s will auction off “the Vivid Pink,” a bubble-gum-colored five-carat diamond with an estimated value of $5 million to $7 million. But instead of scheduling the sale for New York or Geneva, the city chosen was Hong Kong. Asia’s role in the market for super high-end luxury goods is mushrooming. Christie’s and Sotheby’s say that in the last few years Hong Kong has emerged as a top location for sales of expensive jewelry, gems and fine wines...