Use Item Library Unit Cost, Special Order Setup

With this field check marked, the cost of an item with options is calculated from the cost defined in the Vendor Item Library header in addition to the cost defined for each option value that is selected. If this field is not check marked, the cost is taken from the Retail Item Card and the selection of options has no impact on the cost, even for the cost of an item with a fixed option. See also the Vendor Item Library.