Seems totally reasonable. Gas-powered cars cost a lot to fill up and electricity isn't free either, so this totally makes sense. I'd rather go the "pay by the kWh used" route than the "pay the entire expected lifetime cost of charging built into the up-front cost of the car" route, because I know I drive significantly fewer miles than average.
This charge also changes the economics of rolling out Supercharger stations, to the point where they might actually become profitable (rather than being loss-leaders). This means that more of them will be built. That's a great thing.