You may substitute wheat for barley , but there is no logical...

You may substitute wheat for barley , but there is no logical reason to support Cu being a substitute for Zn , the comparative advantage argument you use is also flawed , personally feel you are not making a lot of logic with your statements -no offense
Also Cu was around 60 cents a # back in 1998 so on a long term cycle I bet it is still trading a lot higher now than Zn, a 25% drop in Cu now is of little consequence.
No offence but I think you maybe should finish an economics/business degree before quoting facts that are flawed .