You've probably seen the Disney Princess picture frame series that have a small snowglobe to the left of the frame and a figure of a princess on the right. Cinderella, Snow White, Jasmine, Ariel, Aurora and Tinker Bell are readily available at the parks and are constantly on ebay. I think I saw one sell for as high as $30 once but usually they are around $19-25 range.
Today while going through the closed auctions I came across Mulan which sold for $96. This series first appeared a couple of years ago if memory serves and I think Mulan was part of the original mix but was quickly replaced by Tinker Bell. I'm not sure about that as I wasn't tracking such things back then but I believe that was the case.
Anway the result seems to be that Mulan is rare and in much higher demand then the others.