Rocketman, I used the term "low math" because there's no division or mutiplication involved. If it did I wouldn't have a clue about your figuring.
I'm uncomfortable with your formula because it provides a price before value,and the value of a gun can only be determined by personal knowledge of the gun,not only the physical aspects but historical and maybe personal aspects.
A person who understands what a gun "is about" will have a good idea of its price, and needs no formula.
Maybe your concept is what goes on in our minds while we appraise a gun;in the give and take of our decision process. Here is the true merit to your idea,not in finite figures but in describing how we think.
Make the people who want to know do there homework. Its not hard, its not expensive and its not even that time consuming.
The more you know the better it is.
Justin