I bought a tanzanite & diamond ring last December onboard the Empress of the Seas. My hubby and I wanted to shoot ourselves after looking in many different stores on St. Maartin. After we were back on the ship that night, we stopped in the shop onboard. They were had tanzanite on sale on our sailing. My price was $200 cheaper than what the "preferred" shops in town could do for us. Plus, RCI has a 1 year no questions asked return policy. I don't anticipate returning it, but it was nice to know, I could go back during the cruise and return it if I found something better/cheaper on an island.
Also, the price for the loose stones seems to be reasonable. If you know a jeweler at home that does nice work and is reasonable, maybe you should just consider buying the stone....just a thought. And I definately agree, check prices for tanzanite at home. Also make sure to do some internet research so you know what to look for, cut and the color of the stone. Some places try to convince you that pale lavender is the best, when actually it seems to be the opposite, the darker, bluer is better quality.