The problem is that highways are literally not cheaper but massively subsidized and heavy trucks are destroying that public infrastructure because they are so heavy.
So just saying its all economics when the underlying rules of the game are totally unequal is not that useful.
Sorry I should have been more specific. I'm referring to economics from the viewpoint of the business operating a fleet. Given almost all business do not hold back from whatever incentive and subsidies are available to them, it's fairly reasonable boundary to confine the comparison to.
So just saying its all economics when the underlying rules of the game are totally unequal is not that useful.