Understand that this is just a guide. Prices listed are retail. Wholesale is usually one third to one half of retail. The price a gem will sell for is based on several factors. One is the dealer.
Quality is one of the most important factors in valuing a gem.
Subtle variations in quality can make a substantial difference in the price of high end goods. Unless you are familiar with all the subtle nuances of color, cut, and clarity, per size availability, you will not be able to accurately judge the value of a gem. Few people have the experience to do this accurately and that includes most jewelers. There are no laws or regulations regarding gem appraisals. Many people write appraisals that do not have the experience to arrive at an accurate value.