Purchasing system methods and apparatus are provided wherein a buyer purchases a first product through a purchasing system, such as by submitting a buyer offer. A retailer receives product redemption information from a buyer, the product redemption information enabling the buyer to take possession of the first product. The retailer determines a substitute product to provide to the buyer, the substitute product being different than the first product. The determination may be based on information contained in the buyer offer, such as a product category, a product class and one or more product features.