By no means 'free': there was a $2000 Supercharger access fee included in the purchase price of the S85, or $2500 to enable it after purchase for the S60.
Not available for the S40 variant which wasn't permitted to use the Superchargers.
I am not seeing it. Buying a new S today https://www.tesla.com/models/design offers the following premium options: autopilot - $5k, full self driving - $3k, premium package - $3.5k, smart air suspension - $2.5k, subzero - $1k, hi-fi sound - $2.5k, rear-facing seats - $4k, high-amperage onboard charger - $1.5k.
It seems that once the S70 was released it was removed as an optional line-item across the range and was bundled into the final price. However owners of suitable non-S40 vehicles from before that point can still enable access for a fee ( they have the hardware already installed, it's a database flag change ).
"If your vehicle is eligible, the Supercharging upgrade option will be visible in the Available Upgrades section."
The S40 has the hardware for Supercharging but is excluded by policy.
I'm only aware of this because a friend in the UK has been trying to work-out what's applicable in this market and Tesla's constant changes to the policy makes that difficult.
By no means 'free': there was a $2000 Supercharger access fee included in the purchase price of the S85, or $2500 to enable it after purchase for the S60.
Not available for the S40 variant which wasn't permitted to use the Superchargers.