If they paid for themselves then the DoT wouldn’t have a multibillion dollar highway budget, and that’s not even including all the state funding.

The claim wasn't they pay for themselves but that they don't generate any income. If we want to look at externalities, we'd also have to figure out how much the Iraq war cost.

That is for Capex. Govt can always easily spend Capex, but Opex has to be covered by the users, whether its roads or trains.