$600 price difference.
Remember the rates may reflect different sailing weeks as well as categories of available cabins. Another thing the has an effect on the cruise prices is are the port charges leveed by each port - the cruise lines can not change these.
All I ask is a tall ship and a star to steer her by; John Masefield
Carnival: Glory 2004, Destiny 2008, Splendor 2009, Freedom 2011, Valor 2012, Dream 2013
Celebrity: Summit 2011
Princess: Ruby 2010, 2014, Caribbean 2013, Coral 2014, Regal 2014, 2016, Royal 2017
Star Clippers: Royal Clipper 2015