How can a ban cost less than the market price? A ban is like a giant tax, whose amount is set by fines and jail time in addition to the black-market cost of pr

How can a ban cost less than the market price? A ban is like a giant tax, whose amount is set by fines and jail time in addition to the black-market cost of procuring the thing in the first place (which includes the cost of evading the police and paying for the violence that comes with crime). PS: we don't tax crime and genocides, do we?