As others have alluded, it is difficult to fully asses the costs associated with owning a boat. It has a lot to do with how you use the boat and how well you take care of it. Boats require a fair amount maintenance to keep in good shape. The cost can vary greatly depending on the amount you do yourself or pay someone to do. Make sure you can easily handle the basics which include the items you identified plus fuel.
One thing to remember about boating: There are two good days in a boaters life; The day you buy the boat and the day you sell the boat.
That is not totally true.......but it has some truth to it