http://www.renewableenergyworld.com/rea/news/reworld/story?id=52693

Discounting future commodity inflation, the authors believe that, without additional improvements in end use efficiency, future systems with storage will require $4.5–6 trillion in capital investment at today’s prices to provide generation capacity which supplies the great majority of both static and transport usage. The current cost of imported oil to the USA at $100 per barrel at an import rate of 13.2 million barrels a day – in 2005–2006 – is $482 billion per year.

If number stay at current price then the payback time would be within 8 years... globally, you would to quadruple those numbers… So again, at 150-200 dollars, barrel oil becomes too expensive to use as a form of energy… and big oil is trying everything possible to delay the inevitable...