Interestingly, the claim that: "there is no reason why many citizens and businesses in the EU are not able to send and receive money immediately" is made on the record by the responsible official, Mairead McGuinness, Commissioner for financial services, financial stability and Capital Markets Union.
Which seems incorrect as 10 second payments EU-wide obviously require universal adoption of updated IT systems and more stringent control to guarantee that 10 second deadline.
The increased costs will inevitably have to be paid for somehow, likely via incereased fees.