To add a slight nuance to this excellent analysis, when you sell fine jewellery, the selling price is not the price you receive as the seller, unless you do a private sale. There will be sales commissions and fees that can eat up to 25%, not to mention taxes on capital gains.
ya i think the standard is 5 percent for seller for high priced items, 25 for buyer
but the marketing is worth it
i even saw multi million watches on chinese e commerce website so maybe there are other ways of doing it
taxes are easy, there are many ways to avoid it