That sounds about right for that trip, I'm sorry if you had to pay for it.
I'm surprised they weren't able to be rebooked by the airline either for free or less than that. Who were they supposed to fly with?
Unfortunately, there were no more flights that day with availability. They only had 3 days in Berlin so they made the decision to risk the TGV $$ vs losing their hotel room. I felt so badly for them but the DIL really tried to make the best of it and turn it into an adventure. The train allowed them to see so much beautiful countryside that they would otherwise had missed. Plus, they said the draft beer was really good and helped ease the pain.