 The first Forever stamp went on sale in April 2007. It featured an image of the Liberty Bell and cost 41 cents. The Postal Service developed the Forever stamp basically for two reasons, one being customer ease. Prior to their creation, when the cost to mail a first-class letter increased, people would have to buy one- or two-cent stamps, known as top-up stamps, to stick on envelopes to supplement old stamps. Plus, creating Forever stamps reduced the need for top-up stamps, which cost more to print than they're worth.