There's another level that's ignored here. Some retailers go as far as sending you unique coupons that only you can use and which may or may not be tied to an e

There's another level that's ignored here. Some retailers go as far as sending you unique coupons that only you can use and which may or may not be tied to an expiration date/product EAN. It's just another level of targeted marketing that shows favoritism to repeat customers. If you bought the 1st harry potter book the retailer may send you a unique coupon with a special promotion on the other items in the series if you buy more than 1. Doing it through search urls is just another avenue.