whats a /6 worth

The last three /6's I got rid of went cheap. I sold two at once to a guy for $25 each and the other I threw in with a car deal. I ask and get just over scrap value to keep them from getting junked. They aren't worth a lot of money but they are a fun, neat little engines with lots of potential. Hate to see them get scrapped but don't expect to get rich.