Commodity Markets OXP
An adjustment OXP which splits the marketplaces of stations into seperate ones for buying and selling cargo. The buy price is slightly above and the sell price slightly below the normal station price (~2-5% each way). This is designed to make things a little more realistic, and also to make the trading side of the game a little harder.
This OXP requires at least version 1.81 of Oolite.
Download the current version from the in-game expansion manager.