We have no more of idea what is happening in our game economies than do the talking heads on CNBC
Currency valuation can be either in flux, if you hate yourself, or static.
|Rare||2 x regular value|
|Scarce||1.50 x regular value|
|Abundant||0.75 x regular value|
|Glut||0.50 x regular value|
Devaluation is a scary thing for a Dungeon Master as you can unintentionally ruin the economy of your fantasy city, nation, and world just by allowing your players to find the treasure they so desperately want.