In case anyone thought I was going out on a limb suggesting $6 copper, here's an article where Robert Friedland suggests that copper could go up ten fold...
From the article:

""We're heading for a train wreck here," Friedland said at Bloomberg's New York headquarters. 

He's the founder of Ivanhoe Mines Ltd. and warned: "My fear is that when push finally comes to shove," copper prices might explode ten times. "

and,

"Friedland pointed out that recent acquisitions of mines at high premiums indicate the mining industry is aware prices of the metal are headed higher. He said the tightening of the copper market could increase prices like other commodities in recent years. 

"When metals are required, the prices go crazy and nobody's willing to sell them," he said. "We're heading into that sort of situation."

Even with increasing gloom about the global economy as global central banks tighten interest rates, Friedland remains very bullish on copper. "  (article written in June when rates were still increasing)

https://www.zerohedge.com/commodities/billionaire-mine-owner-warns-copper-market-headed-train-wreck-supply-woes-emerge