The problem with appraisals is that domains market is very dependent on the buyers needs, for example you may have 2 domains that are very similar to each other the first one gets sold for XXXX and the other one for XX. If a company needs a domain so badly they will be willing to pay high. But Domains market still obeys supply and demand rules, for example for some domain types like LLL.com and short generic .com the price is usually very high because of the rareness of these domains, the more rare an item and the fewer the quantity the higher the price will be.
Estibot is rubbish. As I say with all auto-appraisal sites, they are all a joke & use only for novelty purposes only.