Okay, we cruise fairly often. Mostly once a year. Our last three Holland America cruises have had price reduction (s) after our early booking (6 mos to 9 months in advance). All three times we have been able to get our travel agent to get us all or part of that new pricing and still give us the discount that that is offered by her internet/physical agency. We are Mariner members, and get special offers in the mail.

Money Magazine, April 2016 on page 46 talks about some flat cruise pricing on Princess for 7 day cruises since 2013 and some special deals on Crystal (naturally at a higher starting level) Cruises having decreased prices 6% from 2014 to 2015.

I would suspect that the lower prices are a result of low fuel costs, continued stagnation of most economies around the world, the large number of additional capacity coming on stream, and more recently the number of ports that are "hot" in term of security issues and terrorism. So more cabins to sell, lower costs for the cruise lines, matched against less ability and/or inclination to travel by ship. Seniors, a large target market, especially on long cruises, have seen interest rates of saving of nominal levels for a long time now.