This brings me on to my second point. Which is cheaper recycling minerals already extracted, or lunching robots travailing at 25000 mph, moving 1/2 million miles, mining a 2 ton asteroid, repeat until you have a few tons, then launching5 tons of iron back at Earth and losing 2/3 of mass on rentry. This isn't hydrocarbons we are talking about here its basic elements. The reason why iron is more common than than gold is due the laws of physics, the heaver the element the less of it of created by fusion in stars or by super novas. Yes there are vast quantities of minerals out there but they are going to be in roughly the same distribution you find on Earth. In other words you going to find vastly more iron than you are gold. Even at todays prices iron ore is dirt cheap. Even if you do find a 20 ton lump of pure gold, what do think that's going to do the price of gold? The markets can respond quicker than you can get the gold on the ground. The more you find the less its worth.