Here's a thought: If I fly old mate to his property and he gives me a side of beef, no other "payment", is that still Private flight.
Ponder this, to understand how mule-stupid the current rules are: If old mate owns the aircraft, and pays you $$$$$ to fly him to his property, or anywhere else, that’s a private flight in Australia (see CAR 2(7)(d)(i).)
But if you or someone other than you and old mate own the aircraft, it's not private. Same people, same aircraft, same flight, same risks, same understanding of the risks, yet one flight is private and the other commercial.
The classification of operations rules in Australia are mostly about politics and industrial relations.