As a hobby it cannot possibly be "justified" - as everyone has said.
It is no use trying to explain it to parents or partner or girl/boy friend either. If they get it, they get it. If they don't, they don't, and never will. (I personally still find it astonishing that not everybody has a burning ambition to be a pilot).
Another way to understand the OP's question is to think about how the costs can be justified in terms of "How on earth can it be that expensive? Surely I'm being ripped off?" Nope - it really is that expensive, and pretty much everybody in recreational aviation is in it because they love it, not to make money (me included).
Gliding and micros are a bit less expensive and are good routes if you want to get airborne and don't mind the restrictions that go with them.