We're hoping to pull the plug a few years out for a sabbatical (need to settle a few things at home, work, etc. before we could do so). Not yet sure if we'll do a full year or just a winter season. Our thinking is to head to George Town (been there by plane, stayed at the Peace and Plenty, hung out with our cruiser friends, and just loved it). Not yet sure if we would make a B-line to G-Town and then hit the Abacos on the way home, or the reverse.
Anyway, cost of the adventure obviously is a near-constant source of analysis for us. I understand fully that you can do it on nothing or everything, depending on your perspective. We plan to anchor out, have fairly extensive solar panels and a wind generator (not definite on the wind), so hopefully we won't "need" to be shoreside that much or refuel all that often once we get the hook down. That said, we'll be going with our two boys, which means we'll be spending money and/or resources entertaining them (lights, DVDs, shoreside excursions, etc.). We also like to eat out every now and again, particularly when we're in foreign areas, not to mention hang in a bar or two.
We're using $30,000 to $40,000 for the year as our baseline cost for the trip. That excludes insurance, setting up the boat, equipment, clothes, etc., but does include boat maintenance, fuel, entry fees, dockage/moorings for those times when I'm sure we'll be forced to take them, food, booze, entertainment, shoreside excursions, etc. The sense I get is that's a reasonable range, with some margin of error to be expected.
Frankly, I think the biggest variable on the cost will be the trip down the ICW. There's a piece of me that wants to go outside and just get down to Florida, but on the other hand, we've never done the Ditch, and I would like to experience that (not to mention have my kids experience it, though I suspect it might be a bit boring for them). And experiencing the ditch would include at least some exploration of some of the areas we have not really experienced, which only adds to cost.
Anyway, that expectation and perspective explains why I thought $150/week sounded awfully low. But I think your $150 excluded some of the things we mentioned, either because you just didn't count them as part of your day-to-day living expenses and you put them in a different "bucket," or you weren't encumbered by some of the things we will have (i.e., entertaining two very active little boys, and as much as I would like to say otherwise, I suspect telling them that they can't get that ice cream or bag of chips every now and again is not going to play very well).
Thanks Cam, very informative answer, as always.