Just to add a datapoint for people who doubt the claim that rail is more expensive, I travel interstate about once a month and am constantly comparing prices for rail and air. I find plane tickets to be around the same price or cheaper than Amtrak about 75% of the time, and that's been consistent over the last three years or so.
More specifically, I live in Virginia and generally travel to OH, NC, LA, and TX. YMMV, but my experience mirrors the claim.
Flying is cheaper then the train?!? I do not think so; Bring tools and luggage $$, Change your ticket $$, Bring your kids $$, and Pay the new surcharge fees $$. Flying is cheaper then the train ONLY when they have special "teaser fares", but do not change your plans or bring anything!! I have been using the train for business travel and I have seen my travel expenses DECREASE!
In other words, flying is cheaper so long as you know how to work air travel. Change my ticket? Why? I got it right the first time. Check luggage? Without having to pack clothes for an extra day or two on the train I can travel light enough to carry it on easily.
Call them teaser fares, "conspiracy against Amtrak fares," or whatever else you want. Fact is, for whatever reason, flying is often cost competitive with rail.