A jewelry vendor is wise to have their jewelry appraised by an independent certified gemologist who is not one of their own employees. A vendor's own appraisal can be colored by greed whether intended or not. It is quite all right to dicker the price down to the minimum the vendor is willing to get. Keep in mind that, if their asking price is already close to wholesale, there is little room to reduce the price any further. They escaped prosecution by showing that this was a common practice among jewelry vendors.
Prices can vary greatly on similar items from vendor to vendor.
So, lacking an independent appraisal, you should at least shop around and compare prices on items of similar quality. Gemstone quality is a major factor in calculating an accurate value. Get a detailed receipt giving materials, weights and stone numbers, sizes and quality. Also get a money back guarantee if returned within a reasonable period so that you can have the piece appraised by an independent appraiser. If you find that you were overcharged, it may not have been intentional.