I agree with AdrianB1 that I can think of cases where someone will want to do same-day Berlin->Paris->Berlin trip. The ~5 hour total time savings by flight vs.

I agree with AdrianB1 that I can think of cases where someone will want to do same-day Berlin->Paris->Berlin trip. The ~5 hour total time savings by flight vs. train (assuming a frequent enough service) might be worth being less productive while on the trip. If I really need to be present at this "very important" 3 hour meeting in Paris then the best option might be to rent a meeting room at CDG. Then it's a 2 hour flight, 3 hour meeting, and 2 hour flight home - plus transit time in Berlin and going through security at CDG so call it another 3 hours = 10 hours total. While it's a minimum of 17 hours by train.