"All in" costs, which include acquisition of land, geological exploration, permitting, equipment, labor, material necessary for the use and maintenance of the above, remidiation and reclamation, and hundreds of subcategories I have not touched upon can run into the billions $$$ before the first ounce of gold or the first ton of copper is refined.
I, as an occasional small scale miner, understand many of the costs involved. My forays to central Nevada take planning, negotiation with landholders including probable contract review by attorney, physical inspection, sampling, permitting from Federal, State, and local agencies, and a hundred other things before I am ready to set up shop. This is not cheap. While each mine is indeed different, none are cheap to operate. Those gold mines operating under $600 per troy ounce have very rich ore with circumstances that alleviate many of the costs to well below average. The average worldwide is still over $1200 per troy ounce in total costs, which is good when gold is trading at $1600, but is unacceptable at $1200 or even $1300.
Recovery of other metals helps, but is typically a minor boost in the overall productivity.
An advantage to the fall in gold is that I will have less competition for the same parcel of land, wether leasing from a landholder or filing a claim on eligible federal land. Many of the cash strapped speculators will abandon holdings or sell for what was, but a few years ago, below market value.
A disadvantage is that many Juniors that are cash strapped will enter bankruptcy with their holdings tied up in legal proceedings for months, or in some cases, years, thus removing potentially valuable ore from market. While this effect is usually temporary, some areas can be tied up in the courts for several years.
While many here want gold prices to shoot the moon, many that understand any part of the mining industry want stable prices, not volitility, so they can plan for costs, not be blindsided by them.