As a general overview-Most cruiselines require you to book X amount of cabins (8 for RCI, 11 for Celebrity, etc.) and you get one cabin free. So if you book 8, you get 9 for the 8 price. There is your discount-the last cabin divided by however many cabins you had to book to get the free cabin. That does not take into account discounts given by a TA.

Also, TA's, especially large TA's (online or bricks and mortar) often book 20 or so cabins as a "group" and sell them off individually at discounted prices. Try cruisecompete.com. Put in your sailing, how many cabins, and let various agencies bid on your travel. At least it will let you know what is out there.

Unless you are booking suites or have a lot of children, I would think carefully at putting more than 2 adults in most cruise cabins. Small bathrooms which accomodate TWO at best (tight fit), not a lot of storage or closet space. Also, there are limited cabins on ANY ship which have space for 4 adults. Most of the quad cabins are 2 twins which can be made into a queen and a sofa bed. Great for kids, not so great for adults. There are generally very few of the bunk bed type cabins on any cruise ship.

Unless you are students on a tight budget or have a lot of children to accommodate, I would spread everyone out-two adults per cabin, unless it's a suite.