WorldGrower:Economy
Overview
The economy is a web of resources that are used for different purposes.
Inventory Dialog
The inventory is managed in the inventory dialog:

It's possible to view inventory items, execute actions on them, and manage buying/selling of items.
Buying
Using the 'Set buying items', it's possible to advertise to other characters that you want to buy some items.

If the quantity is 0, no items are bought.
If the quantity is larger than 0, up to the quantity of items are bought.
The fact that a character wants to buy something is indicated on that character on the world map.
Selling
It's possible to mark items for sale.
The price can be set using the 'Set selling prices' button:

The fact that a character is selling something is indicated on that character on the world map.