Put something like this in all of your reports:
FEE FOR RECONSIDERATION OF VALUE/REVIEW OF ADDITIONAL COMPARABLE SALES
If the appraiser has erred and the submitted additional sales are are found by the appraiser to be superior to the sales used in this report and their use results in a material change to the appraisal report, no additional fee will be charged. If the appraiser finds that these sales are not as comparable as the sales used in the original appraisal report and the appraiser finds them inappropriate, the client shall pay a fee of $100 for each sale that was submitted to review, plus a minimal $75 inspection trip fee, which may be greater depending on mileage and drive time incurred.