I understand folks think the exact opposite of me and while I kind of see spending a couple hundred for costume jewelry on a whim, I don't see how one could spend thousands on jewelry on a foreign flagged cruise ship. If something turns out to be fake or not the quality you were told it was, you have very little recourse. Maybe folks think X corporates will stand behind their jewelry purchase? If you're spending at least $5K, book a roundtrip to one of the five states that don't have sales tax which are Delaware, Montana, New Hampshire, Oregon and Alaska. Unlike like a vehicle, mined diamonds do appreciate in value but like a vehicle, jewelers will only offer around half that price. If you buy at costco, you can return it for the full purchase price even decades later. Also, many reputable jewelers offer various trade-in options