If you believe this article stamps should cost around 24 cents right now. But the price of stamps keeps rising faster than overall inflation. That is partly because the post office has to support itself with its own revenue, without any additional funding from the government. (Even if the government provided funding consumers would still have to pay through taxes). In a lot of ways the post office operates like a private business, and has to deal with heavy competition from companies like UPS and FedEx as well as e-mail. Recent terrorism threats have increased costs as well. Continuously raising prices might drive away customers, and create a need to raise prices still higher.
The U.S. postal service is getting faster though. 15 years ago sending a letter from the U.S. to Europe took around 2 weeks, whereas now it takes 5 days. While e-mail seems more practical for writing to friends in Europe, it is still sometimes necessary to send tangible letters or cards. But how much will postal prices rise? International friends are becomming more and more expensive.