It appears that the thugs who run the Black Market are not only unscrupulous (they don't give you the preferred customer discount they say they do), their stupid, too (or at least have no understanding of basic economics). If you can save up about 40,000 credits (a lot, I know, but it's worth it), or 4000 crystal, or ore I suppose, you can start manipulating the black market. There's a 5 second update delay in the black markets calculations. I had been exploiting this a bit by buying a bunch of ore all at once if I needed it by holding shift and clicking like mad before the price goes up. This isn't really that big a deal, and would be perfectly OK. The problem is the price DOES go up, and when it does the selling price goes up too. So I can buy about 10,000 or so ore at 500 per or close to it. Then since I just bought a ton of ore, when the market updates, the price to buy it shoots to the max, as does the price to sell it. So I now have 10,000 ore worth 1200 per. Sell it all (or all that I can before the market updates), and I have 100,000 credits. Rinse and repeat as needed. Just for fun I got 100,000 ore and crystal and 1,000,000 credits......

Edit to add: A few ways to fix this. First of all, change the market delay time (this is really easy as it's in the gameplay constants file already) to make it WAY shorter. Also, decouple the selling price from the buying price and vice versa. This would make the economics seem a bit off though. How could crystals be selling for 200 and still cost 2500? Wouldn't make much sense. Lastly, greatly decrease the rate at which buying and selling changes the price. I think this might actually be the best option. Or make the max selling price not much if any higher than the min buying price.