I'm by far from experianced in extended criusing but I think most of the costs are provisions,
fuel, and for those that JUST HAVE TO.. $tay at Marina$.
Eh.. I like being out on the hook and using the self reliable nature of my boat. We have gone 4-5 days without needing to put in anywhere while on Chesepeake Bay. Showers on the boat are a real joy even if they are short.