What is actually the realistic cost. Covering infra, the charger and the maintenance of everything involved. Power and transfer included, with transfer including any standing charges. And after that you probably want decent margin to well run the business.
If you're referring to DC charging it's going to be pretty expensive. The construction and power electronics for a DC station is going to be in the millions.
For AC the rectifier is inside the car and the L2 chargers is just a fancy plug. Price should just be the base electricity cost.