The Wealth of Nations by Part 1 Chapter 10 Page 37

It should follow from all this, that, in the same society or neighbourhood, the average and ordinary rates of profit in the different employments of stock should be more nearly upon a level than the pecuniary wages of the different sorts of labour. They are so accordingly. The difference between the earnings of a common labourer and those of a well employed lawyer or physician, is evidently much greater than that between the ordinary profits in any two different branches of trade. The apparent difference, besides, in the profits of different trades, is generally a deception arising from our not always distinguishing what ought to be considered as wages, from what ought to be considered as profit.

Apothecaries’ profit is become a bye-word, denoting something uncommonly extravagant. This great apparent profit, however,