Train prices go up a lot (a factor of 2 or more) when it’s close to the time of the train, since the price is based on how full the train is currently booked. You might get cheaper train trips by booking further out.

Buses will still beat the cost, but they’re slower and less comfortable.

I've never seen this personally (living in DC area since 2014). At best, flights were on par and you still had to transport from airport to destination vs being likely in the city center (as noted elsewhere in this thread already) and deal with all the other airport time. Bus is definitely cheaper today though with highly variable experience along the way.

If you consider the time-money spent in security checkpoints and riding taxis it’s a wash. Amtrak is able to charge more because it’s a better experience than a flight! But only on the NY-DC route.

Buses on the northeast corridor will certainly be cheaper. Trains (especially Acela) are competing with flying given the huge amount of business travel.