The Wealth of Nations by Part 4 Chapter 3 Page 62

in Great Britain, besides, do not so much seem calculated to hinder the people from going, if I may say so, to the alehouse, as from going where they can buy the best and cheapest liquor. They favour the wine trade of Portugal, and discourage that of France. The Portugese, it is said, indeed, are better customers for our manufactures than the French, and should therefore be encouraged in preference to them. As they give us their custom, it is pretended, we should give them ours. The sneaking arts of underling tradesmen are thus erected into political maxims for the conduct of a great empire: for it is the most underling tradesmen only who make it a rule to employ chiefly their own customers.

A great trader purchases his goods always where they are cheapest and best, without regard to any little interest of this kind.