Inmates mail letters, or send out art or crafts that they made. In some cases, the stamps in circulation were so old that they actually weren't "forever" stamps, and therefore valueless. Such stamps were usually passed off to new inmates before they got wise to their inability to use them and just held onto them until the next bus of eager-but-naive campers arrived on the compound. Occasionally, a more scrupulous inmate would come across a soft, faded 33¢ Purple Heart stamp and just throw it away.
Regardless of how the stamps enter and exit circulation on the compound, there is a continual ebb and flow of supply. For the most part, this works. That is, until a more macro-level event comes along to mess up everything.
On the compound, several predictable, inflationary events occur throughout the year. Mind you, such events don't increase the purchasing power of stamps, just the cost of obtaining them if you actually need the physical stamps. During football season, stamps become scarce on the weekends as bookies and pool organizers hold onto bets and take the "stickers" out of circulation. So if you need to mail a letter or pay somebody that requires "cash" you should plan accordingly. Otherwise, you may be paying $8 for a flat book on Sunday that you could've had for $6 if you bought it on Wednesday.
Stamps are damn near impossible to come by in the days leading up to the Super Bowl. The NCAA Tournament also puts some inflationary pressure on the cost of stamps. As inconvenient as such times are, you can always plan ahead. Moreover, you know that by Monday or Tuesday, everyone will be paid out and you can go back to the normal pricing.
It's the unpredictable "market mover" events that cause more serious problems on the compound... we'll get to those in the next post.