One thing I don't like about PFS is that there isn't an in-game rationale for the way treasure works. I love the rule system itself, but I find it occasionally jars me out of immersion during a session. I like my ruleplaying and my roleplaying to mesh, rather than conflict. So I've come up with an explanation.
I know that this is completely unofficial. I've never mentioned it when GMing, and never will. But thinking to myself that it works this way removes a small impediment to fun, and makes the game a little more enjoyable for me. I'm posting it here in case it might do the same for others.
When the Pathfinder Society sends an agent on a mission, those agents are required to turn over all loot recovered to the Pathfinder Society itself. The Society then rewards the agents in coin. As an extra reward, the Society's crafters make duplicates of turned in items available for purchase by the agents who turned them in.
The Society's motivation in doing this is information. Items recovered from tombs or enemy agents may provide historical information, clues to a vanquished enemy's past actions, or hints about who is supplying an enemy's equipment. This also lets the Society keep any truly dangerous items out of the hands of their field agents.
Of course the Society wants its agents to survive and complete assignments, so it encourages them to make use of resources they find in the field, including consumable magic items. The Society can sometimes glean information from the used remains of a potion, scroll, or wand, or even from broken items, so agents are required to turn in the remains of any consumed or sundered items as well, and the Society also makes copies of those items available to the agents who turned them in.