With enough experience in buying and selling domain names, and enough information about a domain, it's history, traffic, potential buyers, and the seller (all stuff that we take into account, but other services (or DNForum appraisals) do not) -- then it is possible to come up with a good estimation of price.
Here are some recent examples of sales that were appraised, and then shortly after, sold for an amount quite similar:
Fitness.de
Appraised: 24,000 euros.
Sold for: 26,000 euros (this price was negotiated without Sedo's knowledge, before the seller received the appraisal)
BadDrug.com
Appraised: $1,200
Sold: $1,200 (Again, price negotiated without knowledge of the appraisal, and the buyer's budget was 10 times higher).
Adder.com
Appraised: $9,000
Sold: $13,000 with Adder.co.uk and Adder.net
DJ.net plus assets
Appraised: $45,000
Sold: $45,000
These are just off the top of my head; there are many more similar examples.
I thought it might also be relevant to share a few of the comments of happy customers of this "scam" (these are unsolicited comments from our appraisal customers):
"Thanks for your appraisal, I thought it was very
realistic, given the current market conditions."
~Mad.tv
"I also wanted to let you know that I was very pleased with the
quality of your recent appraisal. In addition to applying your
standard model, I was impressed to see that the appraiser
seemed familiar with the domain's target market and used
PPC engines to help gauge demand. The Comparable
Transactions were also quite useful. I will certainly use
your service in the future!"
~PCEdge.com
"I had a feeling your [Domain Appraisal] service would be more accurate, and I was right."
~Sound-systems.com
"Vielen Dank fuer die schnelle Bearbeitung des Wertgutachtens.
Ich bin sehr beeindruckt wie nah Ihr Schaetzwert und der aktuelle Marktwert beieinander liegen. Ihr Gutachten bestaetigt mich die Domain zu kaufen. Ich werde dem Besitzer empfehlen die Abwicklung ueber Sedo laufen zu lassen. Mit dem Kauf und der Abwicklung von joggen.de und workout.de ueber Sedo war ich ebenfalls sehr zufrieden."
"Thanks for sending me the appraisal for hilder.com... Again, you have provided me with useful information. The domainguru one
was pretty much a figure value with an indication of points for various factors. Nothing really to learn from it except the actual value."
~Hilder.com
"Gracias, realmente es una excelente valoracion. Me devuelve la confianza en las valoraciones."
~Brida.com
Beatz, I'm also going to send you an example appraisal for your reference. I think that once you see what we're sending out, you will be better able to see it's value (I am among those people who do not believe in criticizing something that they do not know).
~Matthew