How little would it have to cost or how long would your vacation have to be to compete with a simple rental? Sometimes you can rent for $15/30 a day and I don’t think transporting a whole car would be particularly cheap, given the price of a train ticket in the US.
Yeah, it's possible that it's not economical. I think I'd do it for a $200 SF to DEN premium. I would expect the train tickets for passengers to be cheaper than the flight, though. A flight is currently $150 round trip. And I'd expect a four person room on a train to be approx $400 round trip.
