The Wealth of Nations by Part 5 Chapter 2 Page 246

In the year which ended on the 5th of July 1775, the gross produce of the different duties, under the management of the commissioners of excise in England, amounted to L5,507,308 18s. 8 1/4d., which was levied at an expense of little more than five and a half per cent. From this gross produce, however, there must be deducted what was paid away in bounties and drawbacks upon the exportation of excisable goods, which will reduce the net produce below five millions. The levying of the salt duty, an excise duty, but under a different management, is much more expensive. The net revenue of the customs does not amount to two millions and a half, which is levied at an expense of more than ten per cent in the salaries of officers, and other incidents.

But the perquisites of custom-house officers are everywhere much greater than