I searched for a FlixBus route using the mobile app and noticed that the fare for the exact same trip increased just a few minutes later. Out of curiosity, I checked the FlixBus website and found that the original lower price was still being offered there.
In other words, the app was showing me a more expensive fare than the website for the identical journey.
From my experience, it felt like simply searching for the trip through the app may have signaled my interest and resulted in a higher displayed price. Before booking, it might be worth comparing fares across different platforms to make sure you're getting the best deal.

