This is still a problem if you can charge in 5 minutes.
Throw in a few fast ones for the people who need them and you are sorted. The fast chargers can be multi-head too, so even if someone finishes charging and doesn't come back someone else can still use it. Most rapid chargers are like that.
Also, if it's still a problem with a five minute charge, why doesn't it affect petrol pumps?
Or you glue on half a parking meter to turn the electricity on and off.
Do you have any numbers, or are you guessing?
An average Nissan Leaf battery is about 24kwh (although some cars have much smaller or larger batteries). So if you assume an average Leaf is totally empty, and charging to completely full, that would be a little less than $3 of electricity for roughly 84 miles of range.
To charge a car quickly takes a lot of electricity. But to trickle charge a car takes very little electricity. You can charge cars on as little as 120 volts at 8 amps -- that's less electricity than the average plug-in space heater.
A small parking lot could easily handle 20+ cars simultaneously charging overnight, with just a single standard US household circuit. (100 - 150 amps).
But why didn't you consider other costs, such as equipment installation and maintenance?
And what about the grid? Can the grid sustain the equivalent amount of energy that the nation's cars burn every day in gasoline?
When car parks need to charge hundreds of cars at a time, it will be proditable for them to they will build power providing structures.