These payment channels are handy when you are on some trip and/or use public computer to book your tickets online where there is risk of leaking your bank/credit card details by Spywares.

The disadvantage is that you can't get the left over amount in the card and if you lose it - you lose the amount forever. These cash card charges will be low when booking low price tickets and it'll be only Rs. 1.5 if you book ticket of Rs. 100.

Don't forget to read the summary of bank charges here.