One of the two plugins I’m working on at the moment:
These are the descriptions for several trading related pieces of equipment.
The plugin will allow changing purchase/sale prices via equipment, states and script commands. Thus each trader can have their own prices and trading becomes a viable way for the player to earn money.
As you can see the prices can be changed for particular item types. This means that if you desire so you can only lower the prices for potions or swords or wooden weapons etc.