"The profit increase to the grower is more than fourfold because, as Wyoh pointed out, he now must buy water and other items at controlled high prices. Assuming a free market throughout the sequence his profit enhancement will be of the close order of sixfold. But this would be offset by another factor: Higher prices for exports would cause higher prices for everything consumed in Luna, goods and labor. The total effect would be an enhanced standard of living for all on the close order of twofold. This would be accompanied by vigorous effort to drill and seal more farming tunnels, mine more ice, improve growing methods, all leading to greater export. However, the Terran Market is so large and food shortage so chronic that reduction in profit from increase of export is not a major factor."