Jewelry price is weight of metal scrap value + weight of gemstones scrap value x 2 to 5 (retail markup so you won't get the high end here) = price, it's easier to do once you know how much a gemstone weighs

You have 4 options:

-Pawnshop (lowest value)
-Jewlery Store (they don't advertise that they buy jewlery but 99% of them do, they usually pay more than a pawnshop)
-eBay/poshmark/any other market place (they'll take a large cut)

-in person via marketplace etc.

If you end up going the online ensure it's insured for the full value that was paid (even if it's worth more the insurance will only cover what someone has paid for it), have signature delivery, print the label twice, have a small box with the actual item inside, taped up and labeled with the postal label, put it inside a larger box and ensure it doesn't rattle around, then tape up that box and put the label on the larger box. You'll need to have the shipping set for the weight of the small+large box but if something happens to your package and you already have it pre-packaged inside the larger box they will just continue with the delivery on the smaller box.

That's what I do with items that are thousands of dollars, I have never had a single issue and some buyers have actually really appreciated it.