Presumably she is thrilled, since the ring was valued at a lot more than she paid for it, so if she had bought it in Ireland instead of Bangkok, she would have had to spend a lot more than the 2400 she did spend, for the exact same specification, size and quality of ring!
That's not the value of the ring. The value of the ring is the amount it could be sold for, not the amount you would have to pay to buy a new one. If you want a real valuation, put it on Ebay. The 'saving' you got from buying in Bangkok won't seem so thrilling then.