One tricky bit with a one-way train journey like this is that the train travels all night. So roughly 1/3 of the scenery you go through, you won't be able to see at all. If you have something in particular to see, like the badlands, it might only be visible going eastbound and not westbound.
Three points of advice regarding the "expensive" sleeper car: You pay for food unless you get an expensive sleeper, in which case meals are free. Suddenly that room is not so expensive. A hotel out in the burbs or even in a recreational area is cheap, making the sleeper car look expensive; however I'm avoiding staying in NYC or CHC for a night, and hotel rooms downtown are very expensive, suddenly the sleeper is looking like a good deal. Finally the station in CHC and NYC is right downtown. I've gone to business meetings and training in CHC literally two minutes walk from the station, suddenly not paying for a cab to/from Ohare and pay parking for my car at the airport is making the sleeper car downright cheap... As a room a sleeper car is expensive, as a total systemic cost of the overall trip from home front door and back again, its probably cheaper to take the train with a sleeper cabin than to fly.