A Cause De- Salt Tax and Smugglers

"Salt and tobacco were the most frequently smuggled commodities. Faux-saunage, or breaking of the salt laws, was a daily occurrence in the[areas] where the salt tax was highest...The worst offenders were sentenced to the king's galleys: between 1777 and 1789 the judges of Saumur sent a thousand men to the galleys, while the judges of Reims sent three hundred men between 1740 and 1742 and another four hundred between 1786 and 1789. Everywhere the majority of people convicted...were men, and two-thirds were adults under the age of forty." -France in the Enlightenment

Consider in conjunction with this information the fact that we are speaking of a time when salt was not merely a flavoring or a luxury, but a necessity for preserving food without refrigeration, and even in non-edible processes like dyeing. People had to have it, and to have it they had to pay; but not everyone. Further data also tells us that in some cities the bourgeoisie did not have to pay for their salt.

Going further back in history, Roman soldiers received a salt allowance as part of their pay. This is the origin of the phrase "worth his salt", and also of the word "salary".