siteprice.org is a detailed
domain value calculator and website buy and sell tool.
Calculation a
domain value is not an easy task and there is no way to estimate %100 correctly.
siteprice.org algorithm tries to calculate
value of a domain with gathering,
collecting and analyzing data from several internet resources.
Domain worth calculation differes from website worth calculation if there is no website under the domain name.
So domain name value calculation are mostly based on whois data(domain age), google pagerank, soical media visilibity and backlinks.
Check
website worth calculator topic for more information.