UPI is more like a routing/reconciliation layer like VISA that can work across any bank/wallet, and that core is run by a non-profit government org. It doesn't take custody of the funds and doesn't centralize the information into a private corporation. The fee is also minimal and flat-rate with no profit incentive, instead of paying a percentage of the entire countries transaction volume to some private company. I would guess that adds up to a huge amount of money saved overall.