KJ, you're right there is no challenge to just buying coins. What I was stating was that those who would be giving the challenge coins to those in their units, need to have them paid for somehow. Sometimes it comes down to a commander, CSM, or the like who will take on the Challenge Coin program as an incentive for his unit and just go out and buy them to jump start the program in his unit.
As First Sergeant, our battalion CSM would give me a handful of them every once in a while and if I witnessed a deserving soldier doing their job in a manner that set the standard for the rest of the unit (not just my company) or some other outstanding behavior (ie, high scores on weapons qual. or PT tests, etc.), I would have the option of giving a unit Challenge Coin to that soldier. I would usually present the coin as part of an awards day when many of the families could be present. It was a good morale booster and the soldiers really took to them.