The Wealth of Nations by Part 1 Chapter 10 Page 40

too of, perhaps, fifty or sixty different sorts of goods, their prices, qualities, and the markets where they are to be had cheapest.

He must have all the knowledge, in short, that is necessary for a great merchant, which nothing hinders him from becoming but the want of a sufficient capital. Thirty or forty pounds a year cannot be considered as too great a recompense for the labour of a person so Accomplished. Deduct this from the seemingly great profits of his capital, and little more will remain, perhaps, than the ordinary profits of stock. The greater part of the apparent profit is, in this case too, real wages.

The difference between the apparent profit of the retail and that of the wholesale trade, is much less in the capital than in small towns and country villages.