There are a couple of reasons why the Ultras are more expensive. They are newer and original prices were a lot higher. There are not nearly as many of them. They are more in demand - better suited for the kind of sailing most people do. Have a look at a Classic as well, you might find the double berth adequate for your needs and they are much cheaper. Also the Classic is better in rougher conditions - it has better handholds and shorter distances for moving around inside. A final suggestion re these boats, they are incredibly popular in areas where they became well-established. For example, there was a dealer in CT that sold huge numbers in Long Island Sound and into RI and southern MA. People know and respect the boats there and prices tend to be higher. The other 'hot-spot' would be Lake Ontario. If you find one in an area where they are rare you may get a better price.
Finished the circumnavigation in early February in Grenada. Have to work on a book project for the next several months so the boat will be waiting for next year.