The wine selection at incoming duty free is often nil. On our last three arrivals, there was only a Chilean red...a cab sauv if I recall correctly.
We buy imported spirits for a significant savings over island prices. You are allowed 6 bottles per person.
On the island, we shop for wine at Premium Wines and Spirits. Their case discount is 16 or 17%. They offer free delivery in town.
We get our beer (soft drinks and mix) at the Liquor Shop just north of the roundabout. Their case price is about $10bz higher than the distributor but they have free delivery in town and cheap delivery as far north as Grand Caribe. ...and Norman is a really good guy who is working hard to support his family.