Your shipping cost is $30 (25+5 ins) for EMS or $40 (35+5 FedEx) Both include a fairly high handling fee.
This is the first Chinese dealer that has stated the refund/exchange is inclusive of shipping.
" If there is any problem when you receive your parcel, please contact us without hesitate in 3 days. If you are not 100% satisfied with your purchase, simply return the unworn item within 30 days of the item(s) ship date and we will gladly exchange, replace or refund it inclusive of delivery charges."
Note that you must contact the dealer within 3 days (not 30) and after contacting have 27 more days to return. If you contact them in 4 days, then kiss your refund goodbye.
I'm very suspicious that a Chinese dealer would offer to include delivery charge in a refund, when the shipping charges have a high handling fee included. And only if you are not 100% happy. Which appears on the surface to mean that you just don't like it; not that there is something wrong with the product. That means the dealer would have to pay freight 3 ways.
Returning a product to China (although it came from there) is very difficult. They have to pay duty, and a VAT fee and they're subject to customs delays. I believe they also must have an import account. And if they don't the dealer can delay you and wear you down with the delays, and could finally say that they would not issue him an import account.
Consequently, if you have to return this item you can expect to get a huge run around from this dealer. He may sound nice now, but the tone will change when you want to return something.
I suggest you ask some questions and get a clarification on the guarantee. Save the emails, and don't pay cash. Pay with PayPal where you'll have some degree of protection. Copy the photo from the website and save it in case you have to deal with a dispute through PayPal.
Many people who buy from the Chinese dealers on eBay do not know anything about pearls, and don't recognize when whey receive junk that is worth less than the shipping cost.
Good luck and caveat emptor,
Bill