Earlier today I found this bit of writing on the Castles & Crusades Society fan site. Its available at the Tempest Damnosa blog.
It is a very interesting look at fantasy economics in a way that I think could provide greater depth of encounters between player characters and NPCs. There is a wealth of information here and I suggest that anyone interested in adding more importance to the exchange of wealth and its consequences in their games take a look.
Part 1: Agriculture and the Economy
Part 2: The Unguilded Townsmen
Part 3: Guildsmen of the Town
Part 4: The Nobility
Part 5: The Clergy
Part 6: Feudal Law
Part 7: The Royal Bureaucracy