The advantage of the weighted-average method is that

The weighted average method is used to assign an average cost of production to an individual product. This is useful in businesses where the inventory is so intermingled that it is hard to break down which costs go to which items. The formula is cost of inventory divided by number of units.

A weighted average method is an Inventory costing method. In this method, the cost of the products in the inventory are calculated. All products are assigned the average cost. This method is the easiest to calculate the cost of the inventory by getting the total cost and then assigning the average cost to each item. The advantage of this method is that, there are some products who has complex cost structure and it is usually difficult to calculate the complex cost structure, so weighted average method provides an easy way to calculate the cost of all the inventory items by just calculating the total cost and then assign the average cost to all the items present in the inventory.