We need to associate the cost of an item to the serial number instead of the product. In many situations, we order products from multiple suppliers and each item has a different cost depending on the supplier. Same exact item, different serial number, and different cost.

So we cannot associate the cost of an individual serial number with the cost of the product. It can't work that way. Instead, when items are incoming, their line item cost needs to be related to the serial number. In this way, the sales order margins will not be returned during the creation of the sales order, but only when the item is selected for delivery and that line item is given the serial number. This is fine, as salesmen need not be concerned with margins, only the accountants and the ones who determine the public price of the products.