Orders that include promotions are charged a referral fee on the total sales price after applying the promotion. Total sales price includes the product price and any shipping, gift wrap or other charges.
If a buyer purchases product "A" and gets product "B" for free, then we charge a referral fee on the total sales price of product "A".
If there is a discount on product "A", then we charge a referral fee on the total sales price after applying the discount.