I consider all domain appraisal tools completely counterproductive and, frankly, useless. There is never an accurate way to estimate domain name's value, especially in an automated way, no matter how many variables you are trying to breakdown.
A real domain name value comes from mostly intangible factors. The keyword, how well it plays into the industry, comparable sales, how easy it is to remember, how big the market it serves is, competition, among other things. Most importantly, the domain is going to be worth different money to different buyers.
Bottom line is, never take any estimate from tools like these at face value.