Don't worry -- the cruise lines are well positioned to weather lawsuits of this sort. As someone mentioned, these sorts of costs are factored into their operating budgets. As for fuel costs, those would just get passed along to the customers if they become too high.
If you're interested in why the cruise industry is the most profitable industry in history I suggest you read a book entitled "
Devils on the Deep Blue Sea: The Dreams, Schemes and Showdowns That Built America's Cruise-Ship Empires" by Kristoffer Garin.
In it you will discover why cruise lines pay no income taxes whatsoever, pay their non-officer crews virtually nothing, and force their ports-of-call into extremely beneficial deals for themselves.
In addition, you'll also learn some interesting stories, like how Carnival out manuevered Royal Caribbean in aquiring Princess.