Just my $0.02.
Why would anyone who has the ability to charge at home overnight even think that "FREE" Supercharging is free. Think about your time, both driving there and back, plus your time waiting for the charge. Why would anyone waste 1 to 2 hours to get free electricity that would only cost $3.00 at home?
I came to this realization one day at the Nissan Dealer "FREE" DCFC (L-3) that I would sometime use on a Sunday afternoon when I would drop my wife off at a grocery store a block from the dealer, then drive down, wait for my turn, then plug into the fast charger. When finished I would drive back, go into the store and find my wife, pay for our goods, then go home. Mind you that this store was 15 miles from home. Another one, just as good was less than 1/2 mile from home.
One day as I was waiting my turn to plug in I realized that I was only getting about $1 of electricity, $2 if I arrived at a lower charge level, and thought to myself, "What am I doing???" All this to save only $1 or $2. I never did this again, and probably good that I did not because a couple of months later that Fast Charging station was turned over to EVGo as a paid charging station.
The point with charging using the Tesla Supercharger is that you would only use it while on a trip away from your local area and the Supercharger was the fastest and easiest way to charge. If you think you will be on these trips for say 10,000 miles per year, that is only about $300 to $400 of cost you will pay each year to Tesla, depending on how efficiently you drive.
That means you will pay the same as S and X owners in about 6 to 8 years! Model 3 owners, consider yourself lucky to pay as you go instead of prepay.
Kinda makes me think of why did I prepay for FSD in advance to save $1000 over paying when it is ready. The question at hand is "Will I still have this Model S when it IS finally released?" Our Nissan Leaf, which we thought we would have forever, was totaled by insurance company when we were rear-ended at 3.5 years and 50,000 miles. The good news there is that I was planning to get a new set of tires the next week, so saved almost $1,000 there. jmho