Ever had your phone battery go flat? No signal when you try to check in? Found the app has a bug? Can’t get the airport wi-fi to work? Left your boarding pass at home?
it is reasonable to charge, but the charge should be reasonable.
As an aside, compared to the BA app the Ryanair app is robust and a model of clarity and ease of use. Ryanair may have a vile business model, but it is undeniable that they are very good at what they do.