John made a great point. However, one other thing I thought that should be mentioned is the fact that the higher priced anmals you mention in your original post are probably outnumbered by 10 to 1 by the lower priced animals. In other words, I bet ther are 10 Super Pastels out there for every 1 Super Black Pastel, and the same can be said about BumbleBees versus Mojave Spiders.

Some of the base morphs have become undervalued way too quickly in my opinion. I don't feel like writing a book here, and some more info can be found by searching some other market discussion threads. I just wanted to add that RARITY has to do with price as much as supply and demend (which do go hand in hand).

Hope that helps,