There is also the consideration that the appraisal company may appraise it low in hopes they or one of thier buddies can buy it from you and then resell it.
I tried a major auction sites top appraisal package a fews years back and it was a total waste of money. The 10 points they provided was from a standard template with nothing changed in it to reflect my domain. All just generalizations that could be applied to any domain.
As I was reading I remember thinking how I could not believe I paid for this garbage and how much more valuable the information posted in threads at webmasterworld is in accessing a domains value.