Instead of charging you $5 a gallon, they can even charge $.50 per kWh (or translate it to miles) and that's something like a 3x markup. Even more if they use a renewable energy source.
In my rough calculations, it costs something like $5-$7 to charge from empty to full on my Model-3 mid-range.
And having a charger at the hotel you stay out won't be enough considering how many times I have filled up the tank the night before, but they could still tell that I used gas just driving from the hotel to the airport.
The standard Model 3 has a 50kWh battery, so the cost is roughly $13.
If you charge between 23:00-07:00 the cost is reduced to $7 [2], though presumably that incurs the cost of installing an extra meter. It would be $9.50 sticking with a single meter for house + car.
(For what it's worth, in Denmark the lowest I'm charged is currently double the night rate for PG&E, although the peak day rate is similar. It varies depending on demand and how windy it is forecast to be [3]. But petrol is $2.10/L, so the other commenter's 100L car would be $210 to fill — though at 12.5L/100km, it's pretty inefficient. New vehicles in the US use 9L/100km, in the EU new vehicles average under 5L/100km.)
[1] https://www.bls.gov/regions/west/news-release/averageenergyp...
[2] https://www.pge.com/en_US/residential/rate-plans/rate-plan-o...