As it turns out it doesn’t actually cost that much on regular transit, there’s an AIRPORT SURCHARGE because it’s an “airport train”.
No wonder Americans don’t use public transit, even when the system exists it’s ridiculously difficult and expensive to use.
Depending on state, you may need to defeat varying regional wildlife (at least one full game with multiple generous DLCs, spanning the US) in order to complete the journey, and this does accrue XP as one might expect.
It does also produce players attached to min-maxed builds to adhere to one or another strategy, so play the meta-game carefully.