You have to pay Rs. 10/- first time while applying and for subsequent first and second appeals the State SIC and Central CIC have specified charges. You have to pay accordingly. However no charge exceeds Rs. 20/-.
It depends on individual state rules. Some states prescribed fees for First and second appeals also. Search in google with key words RTI fees in the state of............................. or search in any public authority's website.
Many state governments and Central Governments except with first application, there are no fees for further first or second appeals.