Tesla has priced the supercharger option at $2,000 with the 60 KW-hr battery, and it is included with the 85 KW-hr battery. Let us assume that Tesla is going to deploy 200 SC station nationwide- with 6 chargers each. Each station costs $250,000. Total cost over 2 years = $50M. In the next 2 years, Tesla could sell 50,000 Model S+X, though I think they will exceed that number.
Average Supercharger Capital Cost/Car = Total Cost of Superchargers/Number of cars sold in 2 years
= 50,000,000/50,000 = $1,000/car
If 3% of the cars use the SC/day in the highway, that is 50,000x3%= 1,500 cars. Each charge should be about 50 KW-hr on the average. At 12 cents/KW-hr that is $6/car or $9,000/day or $3.3M/year. Alternately, it would mean about $60/car/year or $600/10 years, approximately.
The Supercharger deployment certainly makes economic sense and Tesla can add sites and chargers every year. It will also be marketing with the big Tesla signs at the Supercharger sites. Now that Tesla has $800M, I expect Tesla to deploy SCs in significant quantities.
The $50M is pittance compared to what the Standard Oil, and others had to spend in today's dollars to explore, produce, refine and transport oil as well as build gas stations all over the US and the world. Comparatively, every house has a "fueling station for the Model S. Just need an extension cord from the washing machine 240V supply to the garage. Hard wiring costs about $100 if you do it yourself. Natural gas is another mess too. Imagine having to compress NG to 5000 lbs, store in fueling stations. BIg trucks need Liquified Natural Gas. Need HAZMAT equipment and training. $Billions in investment.
Now that Tesla has $850M to deploy SC network in the US/Canada, Europe, China and Japan. Cost should not exceed $100M over 2 years. It will indeed drive demand for Model S and X. Once that happens, demand will be ramp up big time, may be at the rate of 200,000-250,000 worldwide for Model S and X. This is disruptive tech, especially the Supercharger.