German ISPs ask approximately 35-40 Euro ($50) to reveal the customer information that corresponds with a single IP address obtained by anti-piracy organizations and copyright holders. Because copyright holders tend to sue tens of thousands of people at once, the total amount of money involved easily exceeds $1000,000 per year, which is unacceptable according to State Attorney General Roswitha MÃ¼ller-PiepenkÃ¶tter (German story).
The copyright holders first go to a criminal court with the purpose of obtaining the customer information of the infringing filesharers. The law enforcement agencies then need the customer info, in order to proceed with the legal investigation. If the copyright holders get the names of the alleged pirates, they start a civil lawsuit.
However, since last week it has become harder for law enforcement agencies to obtain customer information from ISPs. The higher federal court in Germany has ruled that ISPs are not allowed to keep IP-logs without a legal reason (billing for example). This means that users with a dynamic IP address cannot be tracked down if their IP address has changed.