I agree with Donna completely. The $10 a day will certainly be deserved and appreciated. I consider it a fantastic bargain., for the service you receive.
There are many ways that you can cut the cost of a cruise once you are on the ship. If you do not purchase drinks and drink coffee, tea, water and juices, you can save a lot. If you limit or avoid the photos you can save some more. If you don't gamble in the casino or play Bingo, there will be additional savings. If you can avoid the spa, you can save money there.
You can also save money at many ports by booking your own tours or not booking any at all.
The bottom line is to get on the ship and have fun. Spend your money where it will give you the most enjoyment.