Rocky Mountain High! Prime alpine real estate PRICE $15 million. Oscar-adored Michael Douglas and Catherine Zeta-Jones are selling their Aspen homestead. The 664-acre parcel is in Wildcat Ranch, a 6,700-acre tract Douglas bought about 12 years ago. His basic instinct was to save the land from becoming a resort. He and a partner divided it into 14 sites; his has a guest house, a barn, two ponds, and clearances for a main house. Says listings broker Tim Cottrell of Mason & Morse, ''There's a huge herd of elk, bears, bobcats, and deer.'' A far cry from Chicago.