I have no idea what they are worth but you should elaborate as to if your MP-4 was an import or purchased locally from Target. The Target ones were opened and double taped by Hasbro. I bet that lowers the resale value.
I have a list of all G1 characters that have been released in CHUG form. You can find it here. Please feel free to let me know if I got anything wrong so I can fix it.