Can't find anything comparable for earlier years online, so I looked at some old editions of the late Weekender Magazine published by Blue Stone Press, which used to list each home sale bi-annually for every town in Ulster County.
For Autumn of 2004, Gardiner's average price was $345,000. Marbletown's was $340,000. Olive, $301,000. Rochester, $243,000.
For the Spring/Summer of 2005, Gardiner was $281,000 and Marbletown came in at a whopping $481,000. No numbers for Olive, but Rochester was $276,000 and Denning, $365,000.