Well, unlike us, they’re obviously living in a country which massively subsidises energy cost. But it seems they either haven’t done the math properly or their measuring device is broken because even they shouldn’t be paying pennies per month.
You can do the calculation for yearly cost yourself; it’s not too hard. The two variables you need are energy pice and power.
Let’s say you’ve got 30W idle power draw at 0.4€/kWh. That comes out to ~105€/year if you ran it 24/7.