Perhaps you should call the Ketchikan Office
of CBP and ask them. Princess may have a contract right to assess their own fees to cover their having to provide special services to you. The logistics involved, getting CBP to come to the pier, etc. They no doubt want to discourage this type of thing since it is indeed a violation of the law.
I doubt it would add up to $3000 per person. More likely is whoever you spoke with at Princess misread the fine.