If you travel a lot and buy Bus tickets offline, why not try this online, as most of the travels and routes are covered by Ticketvala Homepage and fares too are almost same..
Generally you pay only Rs.10 as convenience charges, and they support all payment modes. What more there are few routes which offer mTicket and so you need not print tickets too!!
Anyways if this was good enough, you even get a Rs.150 discount voucher for your purchase of any tickets at
As there are no details of minimum pay I guess its for any amount of Ticket...

Ticketvala's Diwali Offer

More details of the offer is here and Read the T&C first here..