Any brandable name that you can dream up cannot be worth 24K if there is no other meaning. If it was then all you would have to do is sit around in your underwear and register a few per year and you wouldn't have to work.
Who would go to college? Who would ever get a regular job?
All paid appraisals are scams, and there are no exceptions. Those registrars that are doing appraisals need to have something that pays the bills and they capitalize on the ignorance of the masses.
I would consider calling an appraisal legit if the appraiser would be willing to buy the name off of you for just 10 percent of the appraisal. Since this will never happen then I suggest you take your loss and move on.
An appraisal is the equivalent of an ugly girl asking her mother if she is ugly. The response will never be the truth because its not in anyone's best interest to tell the truth. Any company that charges for appraisals is inherently dishonest and they know it. That doesn't mean that you cannot have your names there, but it does mean that you need to be skeptical about what other type of garbage they may try to sell you. Traffic Blazer, anyone?
As a general rule, if you aren't receiving unsolicited email inquiries about your names then the names aren't that great. That doesn't mean you can't find someone to give you a few thousand once in a while. One man's trash is another man's treasure. Zyan.com isn't that bad, you might have trouble selling it for $100, or you might sell it for $2,000. That's why you need to be a domain artist...to maneuver through it all and get maximum value.