In a couple of posts in this thread, I have seen references to
the "price of production" of gold.   Given that gold is the 
money commodity, referring to its "price" is a bit problematic.
More important, however, is the implication that the product
of any production process could be the money commodity.  Isn't
gold production a "natural monopoly"?  Do not the firms producing
the money commodity have to be natural monopolies? Or, could any 
commodity be the money commodity?
John