It depends on what type of catamaran you're looking for. If you're interested in a cruising cat, check out my guide on the best small catamaran for living aboard. Most of these boats are $100,000 or more on the used market. If you're looking for an inflatable dinghy, Takacat and others make catamarans with high-pressure air floors. These dinghies can be purchased new for around $1,000. In the sailing department, the Hobie Cat is the world's favorite small catamaran, and you can find them used for as little as $500 in some places.