Interesting idea, though I wouldn't like it to be like that. The $5/charge would be an incentive to skip as many superchargers as possible, since every additional charge adds $5 to the travel cost. So it might be cost efficient to sit at a charger for an hour or more and wait until you hit 100% state of charge, to make sure you have enough range to skip 1 or 2 chargers. However, by adding 1 or 2 more charge stops the total supercharging time for the trip might go down to 3 x 10 or 2 x 20 minutes instead of 1 x 60 minutes. This is clearly not good for Tesla and other supercharger users waiting for a free spot.
So the $5/charge pricing may lead to inefficient use of supercharger spots.
I'd prefer $0.x/"minute of charge time". That way, there's an incentive for every paying customer to use superchargers for short times only, decreasing (or preventing) wait times for everyone at peak time. This is probably the best way to make sure superchargers are used as efficiently as possible. The current "up-front" payment for Model S/X supercharging is the best way to get money fast, so new supercharger locations can be added at a rapid speed. Maybe we'll see a mix for Model 3?
I don't really care, as long as I can use superchargers and there are no long wait times. I'm fine with $2000 up-front payment, but prefer the $/min pricing for higher efficiency and possibly decreasing wait times.