I believe that Markets need a limit.
What do I mean by this? Right now, you can sell any item, any quantity of said item, to any market in any world with nothing to stop you. You could, figuratively speaking, flood an entire market with huge amounts of goods you don't need since you just blew up a pirate base, and that planet will accept the goods, no matter the volume.
This, I believe, is bad as it introduces "metagame" plays and bad design such as selling huge amounts of loot to planets / pirate stations then blowing them up when realistically they'd never take that much loot, or planets always printing out vast amounts of money in the form of shortages.
I believe that markets, in order to be more organic in the game, need "limits".
For example, a level 3 planet will have an X amount of cash it can spend in the market; lets say the cap is theoretically 1 million credits. When you sell to the market, it uses this limit to determine whether it can pay you, the player. For example, lets say the market on this level 3 planet has a shortage of 1000 recreational drugs; you fill that shortage and get 500k credits. Now this planet has a coffer of 500k credits left to give. If you do not buy anything from this planet, the coffer remains at a static 500k.
Lets say you then decide to sell a bunch of junk that is worth another 500k to this planet. Then you try to sell some more; you are unable to and all sell options are then removed because there is 0 credits in this market place. You must now either buy from the market to replenish the credits the planet has (for a total cap of 1 million credits since its a level 3 planet), or you must way for 1 ingame month.
Every ingame month, an X percentage of the markets full worth is regenerated. For example, lets say every month 10% of the total market comes back. In this case, every month 100k is brought back into THIS specific planets coffers. This prevents the abuse of low level / low stability planets constantly being money printers because now they have both a soft cap (percentage based being brought back every month) and hard cap (x amount of money per level of planet).
You can still make money but it is much harder as markets are less exploitable through raiding / infinite loops of cash due to level 3 pirates in the system constantly raiding and somehow said planets having infinite cash to pay off all the exorbitant prices you charge them to fix their shortages.