In Australia, public schools consistently outperform private schools, despite having less money.

If you want to spend thousands to send your child to a private school, so that they get a mediocre, spoon fed education, with superfluous 'perks' that don't help their development, and surrounded by rich kids who's privilege will rub off on them, that's fine by me. But the only goof justification is if you don't have a good public school as an alternative. Otherwise you're wasting your money.