Bruce, this is very minor in comparison to the much larger and more important things in your rebalancing efforts but I sure would like to see smuggling get some attention.
tl;dr -- simple change --> illegal (prohibited) goods should sell at a premium on the black market and not a discount compared to prevailing prices in legal markets. Just have the software check the status -- apply the premium if flagged as illegal (contrasted to simply stolen).
Here's the deal: apparently the black market buys goods at ~75% of the price the same goods are going for on the open market. Apparently illegal goods are in the same pricing schema as stolen goods.... when they shouldn't be.
That 25% discount is perfectly reasonable if the goods are stolen but otherwise legal. To use a current day example, a stolen car/TV/computer/whatever sold on the street will be sold for far less than what it can be purchased for from a legitimate dealer. That's why people buy stolen goods (discount); if it didn't sell for less the buyer would simply purchase it from a legitimate seller. Since both thief and vendor have little or no investment in the goods they don't mind selling at a discount since it's still a hefty profit margin.
On the other hand, goods that are illegal are not available from legitimate dealers. They are hard to obtain. But the people who want them really, really want them... whether it's booze, narcotics, explosives, whatever....it's a seller's market. Buyers are willing to pay a premium for them and it's the premium that makes the initial investment (buying in a legal market) and the risks of fines and intervention in getting them to the black market worthwhile.
Illegal goods should be sold at a premium on the black market, not at a discount. Otherwise it makes more economic sense simply to avoid the risk of fines and sell those goods on the open market in a system where they are legal. Leaving aside any discussion of the slave trade, as it stands now there isn't much incentive to engage in game play as a smuggler -- smuggling illegal goods that aren't also stolen (low or zero cost basis) -- as the smuggler is going to take a loss every time, even if there are no fines involved. It wouldn't take much of a premium to make it viable -- maybe as little as 25%. This should only apply to goods that are illegal. Stolen goods that are not illegal should not get this premium but should continue to be discounted as they are now.