I also want to point out, at Least with Carnival no one can sell the cruises for any less than anyone else. Unless is a charter.
Onlines and Sam's Club all have the same pricing they can get through using different rate codes. It does not cost anymore to use a Travel or Cruise Agent if shopping for price.
The trick is finding an Agent and developing a relationship with them. And one that does not book you for SuperSaver Rate at $399 while knowing full well you qualify for Past Guest Rate of $259, or Resident Rates. If you can find a good one stick with them and hold them to the fire to look after you. Soon they will learn to appreciate your repeat business. Even if you are shopping for price
Cruise Specialist aka Carol posted a great example of this on another topic where She helped people that had forgot their Docs. I don't think anyone will be getting that personal attention from the onlines.