There should be very low quantities of these in the market and I would also consider preventing selling altogether, like in Commodities Markets oxp prevents selling when in buying. Or is there some shady black market?
Actually just being able to buy these commodities would be better, will have to look into this. But in all fairness this OXP isn't about buying commodities!
It would be hard to allow buying but not selling. Cargo amounts could be checked and re-added then credits edited as well, but it would likely be a "jarring" manner that's messy and not totally obvious to the player.
Better to just block commodities if you don't really want it.
There is a way to block out the commodities market. Save Anywhere OXP uses such a method to prevent buying and selling at the main station when you're temporarily placed there to save your game.
Unless I set my ship up to act as a Taxi, what reason would I ever have to visit a Taxi station?
I suggested small quantities of commodities (gold/plat/gems) or at least a place to sell some commodities (food, liquors/wines) only as a means of giving me something to do there.
Are there or might there be missions associated with Taxi Galactica?