The phrase you are looking for here is "nickel and diming". To me that's just a term cruisers use who haven't done their research to find out what is included and isn't. With NCL's "Free at Sea" promo ensure, if you haven't already, that you read the Terms and Conditions because it's not completely free, more like sorta, kinda. lol
There are mandatory gratuity charges on the dining and booze packages. Not that it's a bad deal but pretty much all the various lines do the marketing sleight of hand.