First and formost, salt was not only used in the times this game is based in, for flavoring, ingredients, garnishing, or as a means of preserving. It was also used as currency.
The reason I bring currency into this is the fact that it is erroneous to assume people wish only to trade using coin or metals.
Now onto the big aspect. Salt, Honey, Sap, Vinegar - should all have very important, very serious uses in Haven and Hearth. Primarily keeping food from spoiling after being processed or harvested. I believe that food ought to spoil. Except for foods that are preserved, fruits or vegetables dried pickled coated in honey and otherwise kept free from rot. They would take a minor hit in EP gain. but remain untouched by the ravages of time.
This would create value in salt, vinegar, and honey especially. Allowing for salt to be used as currency.
What this means for everyone? Salt mines. potentially containing some metal. more prevailent. And allow a larger number of people to produce cheese effectively.