The net realizable value is basically the price that you will get if you sell (realize) your asset today. Let’s say for example that you have purchased 50 bottles of wine. The cost was $500 in total ($10 each) but they are currently sold at $13 each before incurring $1 marketing and selling cost. The cost (the historical cost) is $10 but the realizable value is $12 (13-1).
Bear in mind that in order to be able to find the net realizable value, there has to be an active market where these products can be readily traded.