What do you want to accomplish as an unlawful? Are you chosing a pirate faction that is gearing towards more political goals? If that is the case you never have to pirate, just hassle authorities and spread propaganda.
If you just want to pirate then make the amounts trivial. I don't believe in charging someone 3-5 million just to stay alive. That is a huge chunk of the casual traders profits and still a decent size of a power-trader. If pirating the was the best way to make money then more people would be doing. I pirate for the RP and there is no sense in punishing another player because I have fun saying "Money or your life, chump." I charge 250k-750k depending on transport size. If someone is empty I scare them real good, but I normally just let them pass.
Also, with mining becoming more prevelant, you can just go to major mining points and have some fun. Whether you leave with actualy money, or just steal some ore, you can still scare the piss out of people.
The next question is how often do you want to fight authority figures? For me a good fight or police rp encounter is just as fun as getting cash from a transport. You can get yourself noticed after one trader and then just sit around and wait for the cavalry. I always try to keep a stock of navy or police pilots in the my hold just to extra piss off johnny law. Sometimes I try to play the hostage game too. Let me leave here safely and I will release my prisoners. I would not recommend trying to hold them hostage for anything more than your life though. A true navy, especially Kusari, would rather shoot the pirate and kill his comrades than suffer the indiginity of surrending credits.
"Hell, there are no rules here--we're trying to accomplish something."
-Thomas Alva Edision
