Domains have no intrinsic value, they are worth what is paid for. The current market for a domain is the number of people that have money ready to buy it immediately, with or without third party advice. If You register a domain for $30 then getting for it $60 is already nice. People who absolutely want a certain domain will pay almost anything. Appraising is just opinion selling business. If You believe in it, then go for it. Keep in mind that some fellow may be desperately looking for a domain like Yours, whatever that may be. A little negotiating may prove far more effective than throwing around value estimations.