1 On average, a jewelry appraisal is going to be based upon the size of the diamond, stone, etc. 2  The cost can be anywhere from $160 to $500 per hour. 3  A 2ct diamond will take around an hour to appraise, while a 6ct diamond may take up to 3 hours to give an appropriate appraisal. The cost can be anywhere from $160 to $500 per hour. 2  A 2ct diamond will take around an hour to appraise, while a 6ct diamond may take up to 3 hours to give an appropriate appraisal.