As Archie pointed out, there are seller who sell sheets of unused stamps at a discount ( his one-third off is a great price). I go to large coin shows where some dealers bring boxes of them to sell for 20%-30% off of face. In fact, the coin club I am in sends its newsletters using these assortments of old stamps.

The fact is that the market for postage stamps has virtually disappeared for the items produced in the millions during the past 50 years or longer.