It really isn't a financial decision. We've cruised the Bahamas for 6 months/yr. for 6 years. Even if you have to pay, it'll be around 50-60 cents. The real problem is without a watermaker you are now on a very strict agenda and schedule. If you're low on diesel, just don't start your engine and wait for the right wind. If you know you need water by Friday, you don't have a choice. You will find your entire cruising schedule is controlled by when and when to get water. Don't come down to the Raggeds where we are for at least three months of the year. Every year someone comes there thinking they can get back before they run out of water. They get caught by the weather and then the cruisers down there have to bail them out.
Consider this: let's say you hold 100 gal of water in your tanks. How long it lasts is a minor part of the problem. Once they are empty and you MUST get someplace that has water, then you will have to carry the water to your boat via 5 gal. jugs. That's 20 jugs of water! Some places you take the empty jug (s) ashore in your dinghy, then walk a ways to get them filled, then back to the dinghy, back to the boat, and then up on deck to fill your tank. Now repeat that process for 19 more jugs. I've seen it take the better part of an entire day. Of course I'm watching from my boat where I just washed all the salt off the deck with fresh water and took a decent shower and am now drinking a rum and tonic using my soda club tonic maker that uses water so I never have to load tonic or soda on the boat nor need to get rid of empty soda cans.
It's not financial, it's a major factor in convenience and what you spend your time doing while in the Bahamas.