A drug dealer testifying at the trial of Silk Road founder Ross William Ulbricht says he sold up to 600 small bags of heroin a day on the site. Michael Duch says he used most of the money to support his $2,000-to-$3,000-a-week heroin addiction.

Duch signed up as a Silk Road vendor in April 2013 under the user name “Deezletime,” USA Today reports. He testified he bought heroin from a dealer in Passaic, New Jersey, and sold it for double the price on Silk Road. He offered 50 small bags of “East Coast style heroin” for $345.69.

He wrapped the heroin in packets designed to protect against moisture, and shipped it in plain mailing containers to avoid the suspicion of government investigators. He offered same-day U.S. Post Office shipping so his customers could get the drug quickly, before they started to experience withdrawal symptoms. Duch says he was soon collecting an estimated $60,000 a month from sales. He was arrested in October 2013 outside of a post office as he was attempting to ship about 25 packages of heroin. He agreed to cooperate with the government.

Silk Road could only be accessed by using encryption software called Tor, which shields computers’ IP addresses, allowing people to make purchases anonymously. Silk Road facilitated more than $30 million in sales annually. It had been online since February 2011.

The website did not use credit cards, instead relying on “Bitcoins,” an untraceable digital currency that is available through online currency exchange services.

Earlier this month, federal agents arrested a man who told them he was a top assistant to the operator of Silk Road 2.0. The site allowed anonymous users to buy and sell illegal drugs, weapons and other illegal items. Silk Road 2.0 emerged as a copycat site a month after Ulbricht was arrested in October 2013.