Marc did a great job of explaining the main types of appraisals. Remembering that craftspeople and jewelry store owners deserve to make a profit is certainly kind. We all have choices, according to our desires and our pocketbooks, thankfully.
If I may point something out about appraisals for insurance...
In order to get a reasonable replacement, you need a very detailed appraisal that will ensure the same type, cut, size, color and quality of gemstone, as well as the craftsmanship of the jewelry fabrication.
Insurance varies wildly in how "replacement" happens. Value can be established by working up the component costs to remake it or gathering data on comparable sales in the appropriate market related to your area of the country. Or, in the case of a jewelry store appraisal, the book retail value without discounts.
If you have an insurance replacement policy based on a brief description on a sales invoice, you may not get an identical replacement. The better the description, the better the replacement.
If the insurance is based on the higher amount that you did not pay, and your insurance is not for agreed-value paid on loss, you will overpay for insurance for every year that you own the item.
Insurers love it when you have a high appraisal, since most policies say they only have to replace it with a like item. More profit at less risk. In truth, many policies have an "out" for the insurer that lets them pay you in cash what
they would pay to replace the item. They have agreements with companies that provide wholesale replacements. Obviously, you would not be able to purchase the same item with a wholesale payment.
So, while insurance companies are not necessarily out to trick you, you need to be very careful to understand exactly what will happen with a claim for loss or damage. Jeweler's Mutual is very good about ensuring that you are paid enough to purchase a replacement in the same purchasing venue, because they work closely with brick and mortar jewelers.
Anyone can call themselves an appraiser, so be sure to find a good one, preferably a gemologist-appraiser. Look for one on the ASA or NAJA websites, or don't insure it at all. Chances are that nothing will ever happen to it if you take good care of it and don't leave it lying around the house.