Upcoming cruises
Oasis of the Seas - February 18 , 2018
Oasis of the Seas - February 25, 2018
Freedom of the Seas - April 14, 2018
Navigator of the Seas - April 22, 2018
I'll be honest, I don't follow your math, but in our example (I'm Diamond) the three free drinks a day for my wife and I (at $12+tax per drink) is worth $594.72 on a seven day cruise. And by going to the Diamond lounge you are not quite limited to just three (thank you staff on Rhapsody!) ...
The Diamond lounge also gives my kids free Shirley Temples and other gifts, and frankly they make them feel like they are the Kings and Queens of the World, and that means a lot to me personally.
The loyalty program weighs on me heavily when I think about trying other cruise lines. So clearly it's effective since I'm normally a cynical bastard. :)