Not sure what the costs are as they are always included in the cost of the charters when we go, but I do know that in St. Vincent it is less for "crew" than for "charter guests" so if you are doing a bareboat charter be sure to say you have crew instead of charter guests, which I think would only apply in a crewed charter situation. The customs offices on St Lucia have set hours posted, but often the officer is late in showing up.
sailn, no need to visit C&I in your case as you never left the country.

Drink all day at home, your friends worry about you; do it on vacation and they say "what a good time you're having". Save your friends needless worry, travel more!