Some napkin math:
Looking up electricity rates in California the industrial rate averages just over 10 cents/kWh while the commercial rate is 13 cents/kWh. Don't know which one Tesla gets. Per the article if Tesla now charges 32-36 cents/kWh for simplicity let's say that is about 20 cents/kWh profit. If a supercharger costs $250,000 to install it would take 1,250,000 kWh of billed charging to recoup the outlay. Assuming an average charge of 50kW (?) per car that is 25,000 charges.
Now I have no idea how long it takes for a supercharger station to have 25,000 charges: If a charge takes half an hour, and a 12 stall station in California is completely full 12 hours a day that would be 288 charges per day, so that is only 87 days? Wow, that is a lot quicker than I thought it would be. (assuming everyone who charges pays of course)