Why do Coupons and Rebates Exist?
"If stores and product providers wanted you to pay the lower price, why don't they just reduce the price? And why do they make the process of getting a rebate so difficult? The answer is, they're trying to price differentiate. Anyone who is willing to jump through hoops to save money is more price-conscious and less likely to have been willing to pay the higher price. In this way, they can get a little closer to charging each person as much as that person is willing to pay. Coupons and rebates are two specific examples of this price differentiation tactic, but you might think of others that are also relevant for your business."
Charging Customers Different Prices for the Same Product or Service
"Perfect price discrimination is the term given to charging each customer as much as that customer will pay. Note that some types of price discrimination are legal and others are not. Some ways you can segment your product line and charge different prices to different subsets of your user base include: feature set, time, interface, convenience, support, flexibility, and completeness. Examples include online vs. offline versions of products, book publishers offering a hardcover and then a paperback, stores offering coupons expecting them to only be used by very price-sensitive customers, and quantity discounts."