Black market
The 'black market' is the trade of goods illegally. Black markets opeate outside the normal ecocomy. The black market is different from the so-called Grey market, where goods are traded legally, but outside the common channels. Goods and services traded on the black market include drug and  arms trafficking as well as prostitution. In some casess, the goods or services are cheaper than on the normal market, because taxes or production costs do not need to be paid - very often the goods traded were stolen. In other cases, the price on the black market is higher, because the goods are difficult to get, producing or handling them may be dangerous. Some drugs are illegal to produce, their price on the black market is often higher than the production costs.