Website Reckon is one of these useful resources that let you have an estimation of how much any site is worth.
Simply by supplying the URL of the site in question you will learn about its estimated value, and you will get lots of statistical information such as its PR, its number of backlinks and its Alexa Rank. You will also learn about the hosting that the site actually has (including its IP Address), and you will get to know how long the site has been around.
As I said at the beginning, tools like this one give you a rough idea of how much any site is worth only. That is, you should take the figures that are produced as what they really are: estimates.
The one information that is unequivocal, now, is the ranking of the site in question along with its number of outbound/incoming links and all the data connected with where the site itself is hosted. That is what you should really pay more attention to.