India, Sept. 21 -- If the volume of transactions is around Rs 30 lakh crore in a single month, then it isn't just a matter of whether or not a transaction is zero cost. The larger question is who pays to keep the system secure, resilient and sustainable. This is what the latest decision by India on the Unified Payments Interface (UPI) means. The new Merchant Discount Rate (MDR) for the specified person-to-merchant (P2M) UPI transactions above Rs 2,000 will be 0.4 per cent with a cap of Rs 300 from Oct 15. Person-to-person payments and payments made by merchants till a limit of Rs 2,000 and under the zero-MDR formula for small merchants will continue to be free. The government's current figures indicate that around 96 per cent of the P2M t...