The Wealth of Nations by Part 4 Chapter 5 Page 5

This, he imagines, upon the true principles of the mercantile system, is a clear proof that this forced corn trade is beneficial to the nation; the value of the exportation exceeding that of the importation by a much greater sum than the whole extraordinary expense which the public has been at in order to get it exported. He does not consider that this extraordinary expense, or the bounty, is the smallest part of the expense which the exportation of corn really costs the society. The capital which the farmer employed in raising it must likewise be taken into the account. Unless the price of the corn when sold in the foreign markets replaces, not only the bounty, but this capital, together with the ordinary profits of stock, the society is a loser by the difference, or the national stock is so much diminished.