Without the date and Train to which you are referring, it is impossible to know the answer for certain. But, it is a safe bet that you are seeing prices for Saver, Value, Standard, and/or possibly Premium (F/J).

There is a pull down menu at the top of each column which shows the specific differences. The cheapest, Saver, have limited availability and, after 24 hours, are completely non-refundable. Flex tickets are refundable. F/J (depending on whether you are on an Acela (F) or Regional (J)) are just that.

Yes, the bus can be cheap. But, it is nowhere near as pleasant as the train.

Only you can determine price vs. value for the various options, e.g., train, fly, bus, drive a car.