[Blurb2350]

That’s the beauty of the “forever stamp”: you never know just how much it costs.

[Jamestown1630]

Yes. That was a very good idea.

[powerset]

I doubt that is the real reason. I think that the real reason is that it is too expensive to produce new stamps every time the rate goes up, not to mention that people would find it very confusing and/or infuriating to use the correct stamps needed to mail a letter *now*, especially if, for example, they had to use two 63-cent stamps on the day the rate went to 68 cents.