RAC/Waitlisted Tickets can also be refundable by IRCTC.Generally IRCTC charge rs. 30 cancellation charge per person for cancelling Waitlisted Tickets.But this can be changed,like I mentioned cancellation time reduce or increase the charge.
If you read IRCTC refund rules you can see that they have clearly mentioned that Upto three (3) Hours actual departure Clerkage charge will be Rs.30 per passenger of train.
Note: (1) Where confirmed reservation has been provided to RAC or Waitlisted ticket holder at any time upto final preparation of charts, such ticket shall be treated as confirmed/partially confirmed and cancellation charges shall be payable as applicable to confirmed/partially confirmed tickets.
(2) No refund shall be granted on RAC/WAITLISTED TICKET against which none of the passengers has travelled, if it is surrendered /TDR filed three(3) Hours after actual departure of the train.