"In July 2017, police forces from several countries worked together to take down the largest drug-trading platform on the darknet, the part of the “deep web” containing information that is only accessible using special web browsers. Before it was closed, AlphaBay had featured more than 250,000 listings for illegal drugs and chemicals. It had had over 200,000 users and 40,000 vendors during its existence. The authorities also succeeded in taking down the trading platform Hansa, described as the third largest criminal marketplace on the dark web.

"It is not yet clear what effect the closures will have. According to an online survey in January 2018, 15 per cent of those who had used darknet sites for purchasing drugs said that they had used such markets less frequently since the closures, and 9 per cent said they had completely stopped. However, more than half did not consider themselves to have been affected by the closures.

"Although the scale of drug trafficking on the darknet remains limited, it has shown signs of rapid growth. Authorities in Europe estimated that drug sales on the darknet from 22 November 2011 to 16 February 2015 amounted to roughly $44 million per year. However, a later study estimated that, in early 2016, drug sales on the darknet were between $14 million and $25 million per month, equivalent to between $170 million and $300 million per year."

Source

World Drug Report 2018. United Nations publication, Sales No. E.18.XI.9.