Cost for Professional Tax Appeal?

How much does it cost to use a professional firm to appeal your taxes?  Many firms will appeal your taxes on a contingency basis with a fee determined by how much the appeal saves you in taxes.  One firm I received information from charges 50% of the first year's tax savings.  This is calculated as the difference between the assessed value shown on your recent notice and the final assessment after appeal.  Let's say your house's new appraised value is $500k and the appeal firm gets the value lowered to $450k.  The assessed value (40% of the appraised value) would go from $200k to $180k, a $20k reduction.  This number is then multiplied by the 2017 millage rate, which is yet to be determined. The 2016 combined millage rate for Fulton County and City of Alpharetta, was roughly .003 (or 3%).  If we use the 2016 number, the tax savings would be $20k x 3% = $600.  So the fee would be 50% x $600 = $300.  Another regional firm charges an up front administrative fee of $250, plus 25% of the first year's tax savings.  Using our example, their fee would be $250 + $150 = $400, but they get the $250 admin fee regardless of whether the appeal is successful.