I'm afraid it does not render a forum useless on the basis that people did not tell you what you want to hear.

Anyway, people make mistakes. Companies make mistakes. I'm sure you've made mistakes in your life too. I certainly make mistakes. Even though mistakes really shouldn't happen, they do.

I think 'forgiving' or at least 'forgetting' is something that will be worth thinking about. Sadly, there are mistakes that cost much, much more (both financially and non-financially), and some of us suffer those things in life and have to move on despite that, because dwelling on it does not make life any better.

If you genuinely believed this was a genuine fare, then I'm sorry you ended up in this situation. If you knew it was a mistake fare and you were hoping it would stick, then you took the gamble and lost. Either way, something to think about: "Is €600 worth so much to me that I feel you need to spend so much time on it?"