If the purpose of the independent appraisal was for insurance replacement and the replacement market comparables were online sales, it would be similar to the selling price. If the purpose was a fair market value and the market was brick and mortar jewelry stores, then the value would be close to the supplied appraisal.
You can't use appraised value to figure out which vendor has the best deal because they have differing standards for grading and value. Look at what people have to say about the vendors on this site.
Try ordering from more than one vendor and compare. Nothing will teach you faster than that.