St. Thomas is in the U.S., not an export market, and there is no difference in destination charge, no different than Hawaii or Alaska. The charge is an arbitrary number anyway although in theory “equalized” regardless if sold in the lower 48, Alaska, Hawaii, PR, Guam or USVI.
Going on a tangent here but that’s not at all true. Cars are generally cheapest in the States. If you equip two identical BMWs, it will be about 25 to 35% less in the U.S. than in Germany, even if that car is being imported from Germany. A German built Audi RS6 costs around $109k in the States...