I think cruise lines are trying to change consumer expectation to higher fares. Not sure if they can hold this line or if they'll reduce fares to fill cabins. It'll be interesting to see if consumers or cruise lines will yield first.
Then again, there used to be more big airlines in the U.S. and hence more competition. Now down to 3 large(r) legacies from 6+. A tighter and more-disciplined oligopoly has emerged.
Very true. There is no advantage (for customers) to having fewer airlines. How's that free market thing working out for us? 
I posted something a few months back about a RCCI (IIRC) exec saying that if each cruise pax spent $2/day more, it'd double bottom line over 5 or so years. Was rather surprised such a small delta (albeit over thousands per cruise) would make sure a large difference.