Also true in many cases in Europe.
You can get a flight ticket for under 20€ between Germany and UK (RyanAir), and have to pay tenfold that for a train ticket.
Or a 30€ ticket to Romania per plane. Booking a train to Romania is much more difficult and expensive and also easily over 100€.
I would wish that train tickets are cheaper than plane tickets, but if you cross country borders, booking train tickets becomes expensive and difficult in Europe.