Unlike some places like Northampton, UK, and Freeport, Bahamas, the cruise ships in Ketchikan come right into town.  This means that there is a plethora of tours and services almost right at the foot of the gangway.  Most of them offer prices lower than available on the ship.  The only advantage of a ship-purchased tour is that there is a good chance the officers will delay sailing if you are delayed, but careful planning can avoid this.