Every port in the game can be classified by one of eight different economy types. The base prices are the same for every port of a certain type.
The prices listed below are base prices. Multiply the base price by the current price index for the port to get the actual price.
Dashes under the Buy column indicate that no port of that economy type sells that particular good.
Dashes under the Sell column indiciate that all ports of that economy sell that particular good, so you'll never get a good price for it there.
NOTE: Some goods will not be available until the port has reached a certain economic worth.