[lava_pidgeon]

Railway is national and cross border is always expensive. For a similar distance you can check Hamburg - Munich.

Europe is too poor to subsidiase long travel trains :p EU policy is more to introduce more competitions into the system / partly privatise it (like it works in Italy)

[brnt]

HSR in France, Italy, Spain can be very cheap. Also, they have generous discounts for 'young people' (up to 30 I think) and 60+.

Living in NL, I have fond memories of the kind of travel enabled by Ouigo when I lived in FR.

[cryptopian]

Another reason is that these routes operate an airfare model where all tickets are for a specific seat on a specific service, with increasing prices as the seats sell out. It allows for more efficient train loading, with the downside that you can't turn up to the station and assume you can take the next train.