the travel agency receives a commisson from the cruise line. If people tell you it's more expensive to book thru a travel agency because somebody has to pay them, don't listen to those folks. It's usually much better to book with a cruise-experienced
travel agent than to book with cruise line directly. A good travel agent should not only be able to find "good deals" for you but he or she should also be able to find the perfect ship and itinerary for you. I would suggest using a CLIA-certified travel agent.
Any more questions, don't hesitate to ask.