I have found that the cost of beverages can be substantially more expensive at the markets, for example the difference in a single case of beer can be ten bucks. You might consider Riteway or Bobby's for groceries & soft goods, and then either Caribbean Cellars or Tico's for beverages. I understand you can pre-order online with them all and have delivered to your boat (or charter base) for free. I usually get a 5%-10% discount simply by asking, if my order is large enough.