First let me say that I know the game is far from finished and that massive balance changes will no doubt occur between now and the full release. The problem that I'm having right now is that the trading system seems completely broken assuming you're not using the black market. No matter how much extra supply a planet has and how much demand there is for that particular good at another planet, profitable trade seems impossible because the price gap never seems all that large. From what I've seen, it's rare that you'll even find a 2 to 1 profit ratio for a particular good.
For example, a planet exports a good for 50c and another buys it for 100c. But even in this case, the obscenely massive 30% tariff makes profitable trades impossible. That 50c cost per unit actually becomes 65c (50c +30%) and that 100c gross profit per unit degrades to 70c (100c - 30%). As such, your net profit per unit is extremely small (5c in this case) and typically not even enough to cover transport costs. On the flip side, responding to events like food shortages results in absolutely obscene and rather game-breaking profits. With a decent trade fleet (7000+ total cargo capacity) I've been able to clear over $1 million credits in a single trade run.
In short, regular trading seems impossible if you avoid the black market and try to remain clean while event based trading is so profitable that you can break the entire economy in a single run. Am I missing something, or does the system just need a lot more balancing?