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