FYI, the website for the cruise terminal puts the price for parking (though it could be outdated) at $24 per day, with a maximum of $180. I'm sailing on the Dawn in June and figure I can't do any better than that from my home in Connecticut. Even for a shorter trip from NJ, $90 each way may be tough to find.
If you're feeling intrepid, there are less expensive garages on the west side a couple miles north. (Google "New York City parking" and you'll find options.) If your luggage is manageable and you're willing to give up the convenience of adjacent parking, you could save yourself a little money -- but not a lot of money.