great rate. but Javitts isn't within walking distance, so we'd still need to add in the price of cabs r/t to get to and from the port.
this is the official port authority site:
https://www.nycruise.com/manhattan-terminal/
it confirms what you saw - 40/night for parking. Also if you click on the parking section you'll read the disclaimer that effective July 1, 2017 no coupons or discounts accepted. ouch!
found that disboards thread:
https://www.disboards.com/threads/just-back-from-dvc-magic-nyc-cruise-any-questions.3551696/
I had forgotten I was the one who started it... It was a dvc member cruise but there is a lot of info and pics of the port and parking etc... beginning on the bottom of the first page. Hope it proves helpful - but I have much more on this if you have any questions.