Seemingly suspended on a "cloud" of stage fog in the showroom of the Imperial Palace Hotel in Las Vegas, this 19-foot 1931 Bugatti Royale, valued at $15 million, is the star of a 550-car collection worth $35 million to be auctioned off Friday and Sunday to international collectors. The Bugattis were built in the 1930s by Italian designer Ettore Bugatti _ mainly for royalty.