Tax value

From YPPedia

Tax value is an element of the sales tax which reflects a standardized price for the tax to be calculated off of. Each commodity (including the three different types of labor) has its own tax value, and the tax cost of a finished product is the sum of the tax values of its ingredients.

The primary effect of this, and the reason the system was changed to be this way, is to make the price of an item the same, no matter where it is produced or purchased from. In particular, this stops shoppekeepers from closing their shoppes to the public, setting the order costs to the minimum, and then ordering goods to sell dockside without paying any sales tax.