Accentnepal I think you hit the nail on the head. That's why your head is hurting
The pool of unsold names is important. So is the pool of private/NDA sales. They are the dark energy of the domain valuation universe.
Then, of course, there is the pool of unregisterd domain names, which is practically infinite.
The vast majority of registered domain names are never sold. Therefore, their value is reg fee by definition.
EstiBot tries to look at the potential value. The way I built my program is that it puts itself in the position of a motivated buyer, either end user or a reseller with great expectations of future value.
It takes the domain name, and compares its characteristics to similar names that have actually been sold. It transforms the domain name into numerical representations of the properties of those keywords (frequency, search popularity, PPC advertising bids, and many more), and of the value of other domain name characteristics, such as tld, hyphens, numbers, length, Then, based on comparison of a large database of previous sales, it performs a statistical calculation, and it gives you a price that it would be willing to pay you for that domain as a motivated buyer.
A price that, given all the data, is most likely (statistics, probability stuff) to reflect the qualities of the domain name in today's market.
This method results in a bias, just like Accentnepal said, towards the values of the pool of previously sold domain names. It ignores the unsold premium names and the unsold and unregistered subpar names.
In my experience, this generally leads to overestimation of the value of low-end domain names, and underestimation of the value of high-end domain names. Generally means just that - not always, but more often than not.
I've built dozens of error reduction routines. Once the value has been calculated, it will be analyzed against various known error sources, such as high Overture when in fact the Overture figure is unreliable. Many more similar routines check for other anomalies in the domain name numerical data. These anomalies cause EstiBot to give penalties, which result in a decrease in the final valuation.
This is why I always say: Great, your domain name was valued at $850. But remember, this is the estimated market price for your domain
assuming it is actually sold. which is like saying, "if you sell this domain it may occur at a price in this ballpark, but if you don't sell this domain, the value is reg fee".
The most important thing is to look at the valuation number as a rough pointer, a quick-look summary of the desirability of the domain name according to EstiBot.
What it cannot do is give you a probability of selling your domain within the next 2 years. I would love to add that to the analysis, but I haven't figured out how to do someting like that yet.