So you got a full refund for the cruise you booked and you will get your next cruise at half price.
I understand you are out some airfare costs and the hotel and other expenses incurred while in Miami.
I don't think you'll recoup your hotel and Miami expenses. I guess in the end what you'll save on your next cruise will probably be what you paid for airfare so hopefully you'll come out even.
I know this is really frustrating and disappointing for you as you were looking forward to a vacation and now you have a headache. But try and look on the bright side, you got your money back for the cruise and when you book your next trip you only have to pay half. I hope you go somewhere fabulous and have a great time. Good luck!