As an MIB Prime collector I have seen a lot of crazy prices over the years, and I say crazy because of how low they go for now. It's like nobody cares about the greatest leader of all time. I recently missed out on the French/Euro Red Feet variant Prime MIB for under $180 !! (thanks to the seller having it finish around dinner time on a week night in our house) I also missed out on a metal plate trailer Prime for around the same price for the same reason late last year.

Here is a good write up from my favourite TF reviewer/blogger Maz. http://www.tf-1.com/articles/mex/mexprime_template.html

But to answer your question, I would say between $150 and $250 which all depends on condition of box, figure etc
Add postage on top of that

I would love to have one.