Prices for travelling by car should contain way more stuff than just gas. There's taxes, insurance, repair and all that nasty stuff that really makes very high costs per mile or kilometer if you do the math.

Though if one already have a car, then it might make sense to use it to get better value from tax and insurance

I'm not sure if I'd agree. This might as well be another mutation of sunk cost fallacy. Anyway, the sooner you sell your car, the higher the price. (ignoring really old and valuable cars here)