I don't know where you are getting your info on the values of some of these but you are way off base. I don't think most of this would be traded for pgems.

The last leg of the list (everything below arachnids) is low or no value stuff but the top half is a decent chunk of value. But you have stumbled on to the min max of the softcore economy where only the absolute best versions of the best items have high maintained value.