How do I determine the market value of a domain name?
The market value of a domain name is usually the average price of previously sold domain names that are similar to the domain name you are interested in. You can find the prices of comparable previously sold domain name on DNJournal.com , DNSaleprice.com and Namebio.com.
As a general rule, .com domain names are priced higher, followed by .net and .org. The exception to this rule are certain country top level domains (ctld) like .co.uk, .co and some other ctld extensions.