There is an application fee that varies for the Centre and for States. For public authorities under the Central Government, this is Rs. 10. For public authorities under the State Governments, please check rules applicable to each state here.
In addition to the application fees, there is also a fee for the information to be delivered (depending on format/number of pages). For the fees applicable to public authorities under the Central Government, please check the RTI Rules, 2012. For the fees applicable to public authorities under the state, please check the individual state rules.
The PIO can ask you to pay more fees for the information but will, however, have to justify the higher fee with proper calculations. The time period between the notice for increased fees and its payment will be excluded from the 30 day period within which you were originally supposed to have received your information