We've sailed much of the Caribbean chain (St Maarten to Grenada) over several winters as guest crew. Since the skipper did the actual clearances this info may be a bit inaccurate but these are our impressions.
Customs fees at the various islands vary but seemed to be $10-20US per person - in some places these fees are reduced if you are 'crew' rather than 'tourist' so it pays to know the local 'ropes' as they say. There may have been a clearance fee for the boat too, can't recall. For so many of these areas each island is it's own country with their own rules.
Most of the marina fees were reasonable by N.A. standards, I think the French islands had the best quality marinas for reasonable fees. In the less populated areas you will often find mooring buoys here and there.. many are 'owned' and (maybe) maintained by a local beach restaurant and often waive the fee if you patronize their business. (The good news with these is at least, unlike BC, you can snorkel and check if their ground tackle is actually likely to hold you.)
The other issue you'll run into is the Boat Boy 'industry'. You'll be greeted - at times considerable distance off - as they compete for your business. They will offer to set you up on a buoy, or offer to help you anchor, or set a stern line ashore. In many cases they will also arrange other things like tours, water/fuel, dinghy watch etc. They do expect a fee for this but generally it's pretty modest ($10-20 E.C. or $3-6US), you are supporting the locals and generating some goodwill. We usually felt more comfortable leaving the boat having used them rather than snubbed them.
Then in some areas you'll get swamped by peddlars.. shell jewelry, produce, and even thinly veiled offers of other commodities perhaps not really legal. Again I think it pays to not alienate these folks, but don't be taken in either. If you buy from one one day, maybe get something from the other the next. Like all such, they can be persistent. You can barter with them and can often trade goods for an old T shirt and a crappy beer!
Restaurant prices vary wildly... but produce is inexpensive. We generally lived a vegetarian lifestyle there unless dining out, and when you see some of the frozen 'meat' available you'll understand why.
By avoiding marinas and restaurants you can live quite cheaply, customs costs of course depend on where you go, how often you move, etc.
I'm sure you'll get better info from some SNers that are there now...
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
Last edited by Faster; 11-18-2009 at 10:38 AM.