Free verbal appraisals for customers is the norm rather than the exception for most professional luthiers. Written appraisal vary widely depending on the area and the amount of detail in the appraisal. Simply saying " I think this thing is worth X dollars" doesn't require much time or effort. A written appraisal with detailed listing of all unique features (instrument dimensions, listing of all visable repairs, cracks, etc) and documenting photos in many cases, requires more time and effort and the appraisor must charge the owner for the time. Like everything else, you pay for what you get.