Free...we were able to buy bottled everywhere in the Bahamas and Caribe and that is what we used for drinking. We did add a PUR water filter to the main sink faucet and used that for making coffee etc. from the tanks with good results...they just don't last that long when the tank water is not up to US standards (I guess that is a good thing!).
After looking at the cost of watermakers and the maintenance issues we decided to go with bottled and it worked out well and a lot less $$ was spent. The other issue with water makers is that you have to leave the harbor you're nicely hunkered down in to make it.