In states where they are registered as an energy provider? A lot. A 10-80% charge will net Tesla $20. Comparatively a gas station that refills a midsize car with a 20 gallon tank will only net $6.
There may be outlier locations, but overall Supercharging is not a big profit center for them. Maybe it'll improve with scale.
Since the Tesla-Supercharging business is running at break-even, you're looking at something like $8.40 for a non-Tesla adding 70kwh. So that's pretty close to your gas vehicle estimate.
10-80% on a Model S/X is 70kwh. Rate billed to customers will vary from 30-50c/kwh at time of charge. Spot in Texas typically ranges from 5c to 15c/kwh. Assuming charge equipment is fully depreciated all they need to pay is maintenance and network cost, which is marginal across a bank of 20 chargers.
70kwh x 25c = $17.50.
Since the Tesla-Supercharging business is running at break-even, you're looking at something like $8.40 for a non-Tesla adding 70kwh.