Okay, so I have done a little homework. I have been researching one of the Carnival cruises (if we decide to go on a cruise). It leaves out of San Juan, Puerto Rico on June 29th and returns on July 6th. It stops at the following places: St. Thomas, Dominica, Barbados, St. Kitts, and the Dominican Republic. You can see it on the Carnival website: 7 Day Southern Caribbean from San Juan, Puerto Rico . Here is a breakdown of some of the pricing I have found (per couple):

Costco: Balcony (8A) $2,083.74 Oceanview (6A) $1,813.74 Inside Cabin (4A) $1,543.74
Expedia: Balcony (8A) $2,282.74 Oceanview (6A) $1,982.74 Inside Cabin (4A) $1,682.74
Priceline: Balcony (8A) $2,477.69 Oceanview (6A) $2,177.69 Inside Cabin (4A) $1,845.69

These numbers include taxes and port fees. Most require a $500 deposit (per couple) at the time of reservation with full payment due by April 2008.

I haven't had too much time to research group pricing, but from what I have read a party of 8 cabins or more usually counts as a group. Sometimes you can get a deal where one person gets a free trip if 8 or more cabins are reserved, so split over a large group of people, you might save $50 each. I can also find pricing on inside cabins if anyone likes (although I wouldnt' recommend one).

I'll try and work on group pricing tomorrow to see what I can find!