I don't even know how to begin to understand what other costs there are besides the stated cost of the cruise!
ps has anyone combined this kind of thing with a timeshare either before or after?
I have only been on the major cruise lines with the larger ships as opposed to Oceana but here are some other gotchas to watch out (and budget) for:
1) Gratuities. The major cruise lines will usually charge about $15 per passenger per day. Of course, like at any restaurants, you can adjust accordingly. Those are only "suggestions". Then there are tips for the baggage handlers when you arrive at the embarkation port. General guideline is about one dollar per bag.
2) Getting to and from the port. How do you intend to get to and from the port? Taxi? Shared van? Limo? Or is there a passenger transfer included in the package you purchased?
3) Drinks on board. Cruise lines tend to rake in the dough for booze. Their drinks appear to be more costly than what you would pay at your neighbourhood pub. Plus, they tack on a 15% gratuity. It's not just booze. Many lines are charging for soft drinks and certain fruit juices.
4) On board activities. If your itinerary includes some full days at sea, you will likely want to do some activities. Some are free, some are not. Interpret that as you see fit.
5) Other non-essentials. While they are not necessary, the cruise lines seem to constantly advertise many goods and services to buy on board including (but definitely not limited to) spa services, salon services, fitness activities, Bingo and casino, photos, etc.
So when budgeting your cruise, please consider all these factors.