Postage stamps are not typically sold at a discounted rate, no matter where you are sourcing or buying them from. Most businesses offer stamps to customers for convenience purposes and a great customer service. They are not making any real profit off of their sale. Buying an entire book of stamps is not practical if you only use one or two a year. The best reason to have them with you always is to avoid asking questions such as where to buy stamps or where can I buy stamps near me in an area you know nothing about. (For those used to postage mailing).