As others have said, it definitely was avaiable to groups over 30 (not sure if it still is). EVERYONE in the group has to participate and pay.
We looked at the option breifly several years ago, and at the time, for a 7 days cruise, if I recall, I belive the price was @ $ 550 Per Person.
$200 per person certainly doesn't like it would be in the ball park, unless perhaps its was a 3 day cruise.