Mostly MDMA, LSD. To a lesser extent weed (harder to transport), coke, heroin, etc.
They do have actual bad things on these sites as well, such as the aforementioned weapons and people, but this is the subsection that we actually SHOULD be going after.
As far as how much; not much. As one other user had posted, one of these illicit markets represents approximately 1/150,000th of the world market. It is a non-issue that the government spends a lot of money on for the purpose of visibility and increased funding (Look at us! We busted the bad guys! We're doing good! Give us more money!).
They do have actual bad things on these sites as well, such as the aforementioned weapons and people, but this is the subsection that we actually SHOULD be going after.
As far as how much; not much. As one other user had posted, one of these illicit markets represents approximately 1/150,000th of the world market. It is a non-issue that the government spends a lot of money on for the purpose of visibility and increased funding (Look at us! We busted the bad guys! We're doing good! Give us more money!).