What is the ruling on a father working in customs dealing with prohibited goods, knowing that he imposes exorbitant fees on them that increase their original price?

The intent of the question is unclear, but the act of collecting customs duties and taxes or assisting therein has been explained previously. If your father prevents the entry of alcohol or reduces its entry through exorbitant customs duties, then there is no harm in his action, as long as it does not lead to another prohibited act.