The Euro is the official currency, although US Dollars are widely accepted.
costs
The hotels, villas, and restaurants are generally not on the "package tour" plans, so deals are scarce - if available at all in High Season.
The Christmas/New Year period is Peak-Season when the Jet and Mega-Yacht set come to the island.
The High Season runs from mid December to mid April, and many Low Season deals are available with significant discounts on hotel and villa accommodation as well as car rentals.
Meals are wonderful, and a number of restaurants will let two people out for under $100.00 for an essentially basic meal two entrees, a bottle of wine, and a salad or dessert or two.
Budget hotel accommodation is available, as well as reasonably priced villas and appartments. However the island does specialise in high end tourism, and the island has some of the best hotels in the Caribbean.