When shopping for jewelry in St.Thomas or St. Maartin, I have found that the privately owned jewelers like, Omni, Ballerina etc will be more than willing to haggle on prices.
The majors, like Little Switzerland, Cardow, Diamonds Int'l will stand firm on prices and are glad to watch you walk out the door. I've bought from smaller independent shops for years and all items purchased are exactly what I thought I was getting. I've never been ripped off. As a matter of fact, I recently took a ring to a jeweler her in Florida to have it cleaned and the first thing he said was "You bought this outside of the USA didn't you". I replied yes and he said it was unique and excellent quality. He also asked how much I paid for it and said I got a good deal.
As far as cologne/perfume goes, I found that the shop on the ship was sometimes a better buy or the same price as the islands.
Waterford and LLadro are exceptional buys in St.Thomas and St.Maartin....just for the tax savings alone if nothing else.
As far as Liquer goes, I've only purchased in St.Thomas at A.H.Rise and the prices are good. There may be places that may be even cheaper but the prices at A.H. Rise are so much cheaper than anything stateside, I'm glad to buy there. They've also never messed up my orders and the boxes are delivered to my cabin on the last day as planned.
I hope this helps! Have a Blast!