Upon every person engaging or continuing within this City in the business of manufacturing, compounding or preparing for sale, profit or commercial use, either directly or through the activity of others in whole or in part, any article, substance, commodity or electric power not produced by public utilities taxable under other provisions of this article, the amount of tax shall be equal to the value of the article, substance, commodity or electric power manufactured, compounded or prepared for sale, as shown by the gross proceeds derived from the sale thereof by the manufacturer or persons compounding or preparing the same, except as otherwise provided, multiplied by a rate of thirty one-hundredths percent (.30%).