1. If you are that convinced it's legit, throw it up for auction and see what it goes for. You could also just list it for some insanely high dollar amount OBO and see if there is any interest.
2. You are asking to find out the value and that all depends on if an item is legit or not. Some people are questioning the authenticity of the item you have presented, which obviously hurts the value and might make it worth nothing.
No one here is out to "get you" and immediately deem something as a reproduction, they are simply trying to help. "Knowing it's a legit item" and asking for a value doesn't make it "legit". I don't know much about this game, but if it's fake, it's not going to be worth much, if anything at all. Good luck.