Welcome to the forums!
How much you will spend can vary greatly based on how much you drink alcoholic beverages and how interested you are in buying photos, etc. For the couples massage and two other nail type services, I would count on spending around $500 (including tip). The average bottle of wine is about $30, beer is about $5-7 a piece, depending on what you are buying and mixed drinks are around $7-8. These are very rough estimates, but shouldn't be too far off.
My wife and I have been on many 7-day cruises together and on average, for the two of us, our final bill is usually around $900-$1,500. Now, keep in mind that we do drink quite a bit of wine and aren't afraid to buy a few photos or utilize the spa. You also need to consider how much money you will be spending while in port. Taxi fares, excursions, etc. can add up quickly as well. In addition to our cruise-ship bill, we will generally spend about $1,000 while in port. Please keep in mind that this isn't required at all, and that figure includes a bit of shopping for my wife.
The bottom line is how much you spend is entirely up to you. You could go on a 7-day cruise and spend only a few hundred dollars, or spend thousands!
Again, this is just my opinion and I'm sure that other folks will have better/more specific information for you, so check back frequently.
Have a great cruise!
Last edited by Wheels87; 10-23-2011 at 04:59 AM.