Just a quick, additional note about currency; there always seems to be just one more thing.
The online campaign recently came across a copper coin that was identified as being more than 1,000 years old ... and sold it for 672 times its monetary value (56 x.p. in my world). This made this one copper coin, normally worth 1/192nd of an experience point, worth 3 experience.
It is worth noting - for those people considering the economics of their world - that while there are a great many things that can be considered treasure, and that the amount of gold or workmanship in the item is relevant to that item's worth, there is also the matter of rarity.
Now supposing that the party had found a chest of such coins, containing perhaps a thousand of them - it would be usual for someone to point out that this haul would diminish the cost of each additional coin. In fact, no. You understand, my world has in excess of 150,000,000 people living on it. The difference between 1 coin, and 1,000 coins, against that sort of potential demand, is negligent. A dealer finding himself with a thousand very old coins would have no trouble selling all of them at a high price. In fact, he could guarantee for himself a higher price, since he could sell a few immediately, giving himself funds to seek out particularly desirous candidates for the coins ... even easier in a world where communications are negligent, and the king of Sweden would be unlikely to know that the sultan of Baku had other similar coins to sell.
Just a thought.