Thanks everyone for your help. There is a lot to learn about pin trading and you are right, I have some that I have, simply because I like them or they have sentimental value, (like the Wonderful world of color pin that I have because we used to watch it every week as kids). I appreciate everyone's input and have been doing as much reading as I can find. I will look up that book, but it is interesting to know that pins can change value so quickly. I just assumed that they would go up and up, not down.
Obi-wan-pinobi, it was the MGM Motor Parade Monsters Inc. #8560. Apparently according to the cast member, something was cut out that wasn't supposed to be on a limited number of them and then it was corrected. When researching Pinpics, the only pin they show, looks just like the one I have, so I don't think it is a mistake pin.
Cool Disney Cat, the pins I was unable to find on ebay are just older pins I think. They were rack pins or freebies from somewhere that I traded for because I liked the way they looked. None of my pins have numbers or anything special on the back of them. I will keep watching ebay and maybe they will show up.