Justify the cost of learning to fly??? To whom? Either YOU want to do that or you don't!
If someone who is in control or influence over your income / wealth calls it into question you should wonder whether they are in control over your life.
In aviation there's a saying - "if there's a doubt, there's NO doubt - don't do it."
Either this is something you can afford to do and will afford to go on doing after you gain a licence, or STOP NOW! Too many gain a licence and stop flying within a year or so. That's a waste of money.