They're knida cool, I have one because I like unusual complications. $80 is about right in nice shape. http://www.hodinkee.com/blog/2009/6...-perpetual-calendar-thats-time-is-almost.html
As long as it runs and sets ok it seems like a fair price. They look like they are going from $60-$250 on ebay depending on condition, original bracelet, etc...