Mike - you have created a identity that many will try to emulate, but none will be anywhere as good as you are! You are the one and only!!
As far as worth goes...many want your plug for the sheer single genius of it. I for one will hang it to show all what a true master craftsman you really are. There is no way to put a monetary cost to a work such as yours. If you really wanted to put a price on that work of art you would have to hold an auction, but you would only find what the highest bidder at the time would pay not what it really means to serious plugmakers.
