Oil, copper, etc are economic imput goods, and there is a price level beyond which people will switch off, will not buy: try $500 oil now, and I bet a lot of people will by going to work on bicycles.
There is very little economic use for gold beyond its monetary reserve asset use. Today the main buyers of gold are central banks keen to preserve their balance sheet ravaged by declining bond and currency values. There is no price too high for the central banks to buy gold because there is no limit to the quantity of their own currency they can print. Pushing up gold price to absorb inflationary pressures also serves a useful purpose. They can not do that with oil.
