Once you tender to the island you have to tender back - $1.50. $1.50 x 3000 passengers = $4500 x 52 weeks a year = $234K. That is for one ship.
But let's face it, just like tips, costs need to increase. None of us wants to work for pay that will never increase.
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
Sail Windjammer: Mandalay 2017
Star Clippers: Royal Clipper 2015