" We thus see that the price of a commodity is indeed determined by its cost of production, but in such wise that the periods in which the price of these commodities rises above the cost of production are balanced by the periods in which it sinks below the cost of production, and vice versa. Of course this does not hold good for a single given product of an industry, but only for that branch of industry. So also it does not hold good for an individual manufacturer, but only for the whole class of manufacturers. "

― Karl Marx , Wage-Labour and Capital/Value, Price and Profit