Missing the point

Yes taxation rates matter. But France-Spain and France-Belgium trains are expensive to take *because the capacity is too low*

If you reduce ticket prices on those routes you WON’T TRANSPORT MORE PEOPLE. Just different people. As the trains are full anyway

So, Clement Beaune, how are you going to get more TGVs to Barcelona?

https://www.euronews.com/green/2023/08/10/france-is-raising-taxes-on-flights-to-pay-for-trains-should-other-european-countries-do-th

Why are flights cheaper than trains in Europe?

Train travel is often more expensive than flying. Could taxing aviation to invest in the rail industry help change that?

euronews
And if your response is “ah but rail firms will add more capacity”, I’d point you to Thalys that hasn’t upped capacity in 2 decades despite rising demand and sky high prices. And SNCF that runs just 2 TGVs to Barcelona a day. Both easy to solve, both not done.
@jon This! Yet I remain marginally hopeful that public pressure can occasionally work: the budget for traditional low income (?) tourism SNCF night trains to the south of France got reinstated over uproar. Last year we even enjoyed new cars with comfy beds. But it did get pricey. Probably need EU level pressure for more capacity, but current German government a major detriment there. Sigh.
@jakob That was a job retention effort for a SNCF works in Perigeux to renovate those vehicles. But yes, public pressure made it happen - and that’s welcome.