When buying expensive watches, the truth is your savings would be in not paying sales tax and getting it duty free - at least initially. For instance, Rolex sets the retail price because they don't want to affect the value of the product with dealers undercutting each other. Get caught discounting and they will lose the rights to sell Rolex.
Another interesting point about Rolex - I've been told it is a trademark infringement to enter the U.S. with more than one Rolex in your possession. I've been told Customs could confiscate any of the extra watches.
Most high end watch manufacturers don't want local competition, and for that reason there is only one authorized Rolex dealer on St. Martin although they have stores on both sides of the island. I expect the same is true for the other brands.
Bottom line - you can save a few hundred dollars. Personally I buy my watches locally. I may be paying more but I know they are legitimate and if I have a problem they are 20 minutes away.
I am talking a lot about Rolex because that is what I know about. Lately I've become a bit jaded about that brand because I've had problems with my Rolex watches. I still can't get one to work and another loses time. Of course taking them to be repaired is like taking your Porsche in for an oil change - it may be a simple thing but it'll still cost you a few hundred dollars. Plus, Rolex is the most copied and thus there are a lot of fakes out there. I'm thinking of moving towards other names, which are also less expensive and perhaps more accurate.