The cruises for a 7 day round trip from Seattle to Alaska in end of June this year go up from around $800 per cabin which sleeps max 4 people. And you better book early (like 3 months ahead). The group discounts usually come with minimum of 8 cabins reserved, and the group could receive about 6% discount. Reputable travel agencies who deal often with cruise lines with large volumes may purchase blocks under their special group discounts which are then passed on to individual customers. Group rates typically are not published publicly. So call cruise lines or travel agencies including online travel agencies to find out more details.