Alex Taborrok: Many people think that price is determined by historical cost. Price is never, ever, determined by historical cost. Price is determined by supply and demand. If supply or demand change then the price changes regardless of historical cost. Last year's fashions? The price falls regardless of cost. Chopped up dead sharks? If demand is high, the price is high regardless of historical cost. If the demand for gas were to suddenly fall, the price of gas would fall too, regardless of cost. In the present situation the supply of gas has been reduced and the price has gone up. Historical cost is always irrelevant.