NYC to Chicago probably has a decent customer base to support that price point. For amusement, try Miami/Seattle via Amtrak. It's possible, since I looked up the route [1]. One week transit time one way, at $2,000 (I don't recall if the price was round trip or just one way). And trying to work on the train was fun (too "swishy" to use the computer:
http://boston.conman.org/2015/08/05.2). Totally not worth it for me. Sadly [2].
[1] For reference, I live near Miami (technically, I live in Boca Raton, but Miami is "close enough" at this scale). The company I work for is based in Seattle. I refuse to fly anymore for a variety of reasons.
[2] Riding in a private rail car really spoiled travel for me: http://boston.conman.org/2015/08/05.4 But way out of my pay grade.