First of all, stored value payments should be a lot faster than post-pay payments. Infrared payments might also be faster than cash payments, resulting in a saving of time.
But costs could also be reduced. Nowadays, retailers must pay a fee of 2 to 7 percent of the purchased amount to the credit card company. The fees for digital cash transactions are likely to be smaller than for today's cards because of smaller operating costs for the issuer.
There would also be less vandalism, since with infrared interfaces, there are no slots or contacts. Ticket vending machines could use electronic receipts rather than printers. This would reduce maintenance costs.
In general, infrared terminals should be cheaper than stripe or chip card terminals and won't wear off as fast.
Vending machines would not need tamper resistant modules except if aggregating totals.
Of course back office costs for counting, storing and transporting cash would fall away.