In summary: There are no fixed fees for appealing an iScore report across all banks.
Key points
Check your bank's current fee schedule and inquire about each cost associated with the service, not just a single fee.
If a fee has already been charged and you don't understand it, ask your bank for an explanation before filing an appeal.
The figures, fees and limits in this answer vary by bank and change over time — confirm them with your bank or the official source before acting.