what is the impact to revenue recognition if the cost is upated to 0

We have items which is extra warrenty. The items are on PO as well as sales orders as we purchased the warrenty from supplier and sell them to the customer. Previously, the item is set with a cost, which is the same as the list prict. In this case, upon the shipment of the sales order, the GL entiry will hit COGS and inventory account. Accounting does not want these items to have impact on COGS and inventory account so we decided to update the cost with $0. In this case, upon the shipment of the sales order, $0 will be charge to