The mistake the former person made was in going to Great Domains - seriously, never pay anything above $20 for an appraisal as whoever you have doing them, they'll always still just be one persons opinion - albeit an experienced person if you choose the right companies. If you really are going to go the appraisal route always get at least 3 different opinions, thats the only way to ever really get an accurate median price because one appraiser might have experience of a certain area, or notice something about a specific domain when another will not.
It is unfair to tarnish all Domain Appraisal companies with the same brush. Yes, it's totally true that some (if not most) inflate the prices to make their customers happy but then there ARE some domains that are worth the big bucks, even nowdays. As an appraiser i might give a high price for a domain because i know it would be popular in a certain area or appeal to certain companies but the owner might have no idea how to sell a domain name, approach it totally the wrong way and end up getting $500 for it ..... doesn't mean i was wrong. I guess then we get onto the good/bad points of domain brokers but it really does just boil down to who you choose to go to and how good they are.
An appraisal is just one persons opinion, although you might be lucky and get a financial analyst with experience in the area, or somebody who has done thousands of appraisals and sold high value names in a variety of areas but 9 times out of 10 it's pretty much just a more detailed and more researched version of an opinion you would find here. Thats not to say they are worthless though - companies seem to like you obtaining a number of independant opinions and have something presented to them that backs up your own opinion and doesn't look like a forum print-out. You get what you want out of it - for under $20 you are getting someones opinion, and having them do all the search and statistics work for you. You can do it yourself but thats not bad. Personally, i tried a number of professional appraisers in the past - some inflated prices, some were honest and some gave out great information that i wouldn't have discovered elsewhere and in some cases (though it was rare) i ended up selling the names for higher than the appraisal prices but i definitely found they helped when approaching prospective buyers.