IMHO the only way to make it workable for everyone is to charge by the kwhr. The way I figure it a cost of $0.50 per kwhr would be the maximum that I would pay to charge. Anything higher and it is cheaper and easier for me to take the ICE car.
In my case, it cost me $0.11 per kwhr at home. Away from home it cost me my TIME. Today my wife and I were driving around and ended up going about 70 miles, mostly on the freeway but lots of street driving also. Since we limit our charge to 80% this was about all we could have done ending up home on empty. However, since we did not know how many miles it would end up being, during the early afternoon I dropped the wife off at the grocery store while I drove another block down the street to the Nissan dealer DCQC. We had used about 25 miles by this time so I spent 15 minutes on the charger to get me back to 80%. At home the 6 kwhr would have cost $0.66 but since I got it free, it cost me 30 minutes of my time (5 minutes driving each way, 5 minutes waiting for someone else to finish, and 15 minutes to charge). I got back, parked, and found her in the checkout line.
Why would I drive out of my way to find one of these L3 DCQC's to pay $7.50, $5.00, or any other per charge rate that is more expensive than gas? Even if I needed 12 kwhr charge, at home that is still only $1.32. Why spend all that extra time to charge if it cost as much or more than gas with the other ICE car?
I understand they have overhead to be paid for in addition to the cost of electricity, but as was stated above, this was all paid for by taxes already. Now they only need to pay for maintenance and admin. If the price was reasonable then more EV drivers would use these charging stations rather than them sitting unused.
We now have about 7,000 miles on our Leaf in just under 6 months. To date the only charging we have done, other than at home, has been at Nissan dealers for a few trips, and the dealer we leased it through on days like today. We have NEVER used any of the Pay sites, even though we got the cards when we got the car (just in case). Why waste my time and pay $5.00 or $7.50 for something I can get for $1.00 at home and not waste time?
Above when I stated that the most I would pay was $0.50 per kwhr did not mean that this is the price I recommended. If it was anywhere close to what I pay at home then the price would be acceptable. Anything above that would make me unhappy up to the max at which point I would rather take the ICE.