Guys these are just automatic valuation based on domain sales history, age, keywords and backlinks e.t.c and is not accurate.
There is one auto appraisal service www.estibot.com which is known to give more accurate results although in that case too don't take it seriously.
If you seriously want a value of your domain then get it done from professional domain appraisal service. In that case a human will look into you domain and then value it. It costs money though although there are a couple of start ups who provide free appraisal.
Or you can post in domain name forums like namepros.com, domainstate.com or dnforum.com(registration not free) and the members will give you input on on the value of your domain. They have separate subsection by the name of DOMAIN APPRAISAL on forums for this purpose.