Clear answer: Bend over and get ready.
These types of promos are for one reason: To benefit the promoter, end of that part of the conversation.
If you are not worried about being out the fare for the person that qualifies for the cruise and if you really want the cruise, don't be worried about the difference in cost, besides if you have to worry about the cost you shouldn't be on a gambling cruise anyway. Plus if it is within the next 30/60 days you aint going anyway. If you are in possession of a final payment invoice and have boarding passes in hand you are good to go as far as the cruise line is concerned, all necessary fares have been paid or you would not have boarding passes, unless the promoter has not paid the cruise line. In the meantime you really need to do some serious homework
These deals are not really scams but they are close enough that if you have any hair on the back of your neck it should be standing straight up.
I have lived in Nevada for close to 40 years, spent several of them working in casinos so after several posts over time from people wanting to sell there interest, cut deals for special buy ins, and on and on I have contemplated looking more seriously into these so called deals, so thank you for triggering an enzyme to make me get serious and see what these deals are REALLY about because all the posts that I read are from people that seem to get caught in a position/situation that they either need 911 help or they are willing to practically give their investment away just to get out of it for one reason or another and it is usually because the person with the comp can't go, besides my boredom hobby is chasing internet scams so thank you again, you woke up the sleeping giant.
Of course at this point for lack of research this is all speculation on my part so your decision needs to be based on your own experience with the company you booked this cruise with.
This wouldn't happen to be a gambling cruise out of Port Canaveral would it?