How do I assess the value of tradable goods for zakat payment?

Tradable goods are assessed at the end of every zakat year according to their current market value rather than their historical cost basis (i.e. the original price of the asset). The current market value of tradable goods is measured as their market value if all the goods were sold at once, rather than if they were sold individually at their retail or wholesale price, entailing a higher zakat amount; it is superior, though not obligatory, to measure the current market value of tradable goods at their individual wholesale price.