[n4r9]

It must depend on the cities and how far in advance you can book.

I just checked on Amtrak and you can get a train from Seattle to Spokane for $37 in July. This website suggests a comparable cost for driving: https://www.travelmath.com/cost-of-driving/from/Seattle,+WA/... . That seems to be based purely on fuel costs, not counting the marginal costs of insurance and maintenance.

Using the same method, I can get Amtrak from Seattle to Chicago at $169, vs $300 drivings costs.