Kiwi Stamps

I buy self adhesive stamps in boxes of 100. The Kiwi stamp does not have a monetry value. It always covers the cost of a standard domestic letter. When these stamps were first released about 10 years ago postage was 50c. With postage now at 80c there would be a saving of $30 a box had one bothered to hoard them and wait for postage to increase. But who does that?