A while back, Tesla said they were going to stop giving lifetime free charging with new (2017) cars, and switch to an annual allowance with top-up fee for use of their chargers.
Today, they announced the pricing: £0.20 per kWh, in addition to the 400kWh per year included with the car.
1 kWh gets you 3.8-4.2 miles on paper (probably closer to 3, real-world) on a Model S, and a full charge from empty at a Supercharger will be between £12-£20 depending on the battery size in your vehicle (for "253"-"381" miles of range)
Thoughts? 5-7p/mile seems reasonable to me, and it's not much higher than the UK average of about 12p/kWh to charge at home