If any person liable for any tax under Section 727.09 or 727.10 ships or transports his products or any part thereof out of the City without making sale of such products, the value of the products in the condition or form in which they exist immediately before transportation out of the City shall be the basis for the assessment of the tax imposed in such sections, except in those instances in which another measure of the tax is expressly provided. Council shall prescribe equitable and uniform rules ascertaining such values.