Currency in Saint Barthélemy to euro (EUR €). For 10 US dollars you can get 8.95 euros. For 100 US dollars you can get 89.5 euros. And the other way: For 10 euros you can get 12.1 US dollars.
And if you plan a trip to a given region of the world, maybe cheaper than in Saint Barthélemy will be in nearby countries? See prices in: Anguilla, Saint-Martin (French part), British Virgin Islands, Saint Kitts and Nevis, and Virgin Islands.