I have not done a sober cruise. I imagine like many group cruises they would be more expensive than a "normal" cruise because the non-drinking passengers would have to make up for the income lost by lack of bar sales. Christian-themed cruises are an example of this.
Many cruises have meetings of Friends of BillW (is that right).
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
Star Clippers: Royal Clipper 2015