Fantasy economy: how to design a deep, sophisticated crafting system?

I want to construct an immersive, complex and functional fantasy economy in order to inform my world-building process. I’m interested in finding a working economic model and applying that into low-tech, low-magic environments, similar to the authentic late medieval/early modern eras.

  1. What sorts of commodities and raw materials are out there and where to get them? A list of commodities would be great.
  2. How does trade and transportation (land and water) work, and what are the possible pitfalls of trading (taxes, bans on certain goods, robberies, etc.)?
  3. Crafting! How would you proceed in creating this sort of a complex, multilayered system, where raw materials are being converted into more polished materials using various vocations and techniques (which ones?)? How would you design a crafting system, where these commodities and materials are used to assemble finished products? How to fit in the price of labor, and the skill of rare artisans?

I’m looking for something of a complexity along the lines of the economic system of EVE Online. However, EVE Online is a computer game, and science fiction besides. I’m looking for something more varied, middle age-ish, with a personal touch, and that can account for differences based on the cultures participating in the whole trading system.