Can you justify flying?
No I can't.
Neither can I justify going out for dinner, playing sports, spending time here on proon, going on vacation and a lot of other things.
But that's the beauty of "free time" and "disposable income". You don't have to justify what you do with it. Just spend it any way you see fit.
Of course flying is rather expensive compared to a lot of other possible hobbies and I have promised myself that if I cannot find the money, or the time, or the motivation to spend at least 12 hours each year flying, I will quit and not regret it.