I have never heard of such a thing once final payment has been made. Only if you haven't made final payment have I heard of a change in fare being worked out if prices went down. But even that is not automatic. Think about it. If they refunded everyone who paid more they would be better off in most cases never decreasing fares when they know they won't be full for a particular sailing. They would be better off in many cases sailing with some empty cabins. Between the higher fares they collected for the small amount of cabins and the less cost of provisions since less people are onboard, they might actually be better off not decreasing fares to fill up. Perhaps if someone made a big stink they will give some kind of credit one on one, but what anyone pays for a particular cabin is often different than what someone else paid for the same cabin category on the same sailing. You don't hear of airlines giving refunds to everyone who paid more when they decrease prices after someone has purchased a ticket. And we all know everyone in coach seats often pay different fares. To tell the truth I think sometimes they are already shooting themselves in the foot by decreasing fares so much. Now some sailings are so full with too many people stuffed into some cabins, that it takes away from the cruise experience of some and they may lose future customers.