Do Japanese ATMs Price Discriminate?

In Japan, there is an extra charge of ?100 (about $1.20) if you withdraw cash from an ATM evenings or weekends. One wise-guy friend suggested that perhaps this is to give the capital equipment the same overtime pay as received by workers. Seriously, though, the only possible cost-based justification for this price discrimination in ATM usage is that workers might have to make sure the machines don’t run out of cash at those times, and their labor requires overtime pay. But surely the same thing is true in the U.S. and Europe, and I don’t see this ATM surcharge there. A more likely explanation is demand-based price discrimination – the banks realize that people have fewer alternatives (no bank tellers available) at those times and price accordingly. Maybe – but the biggest cost to banks is tellers’ time, so I should think that they would do anything to encourage ATM usage, regardless of time of day or week.