I know two people who are currently studying PPE at UNSW (I also did consider it as a choice once upon a time); one is transferring out to Law/Eco and the other is transferring out to Comm/Eco (they both decided on this after one term) especially since they don’t really go into a lot of depth with either of the three (politics, philosophy, eco). If you’re interested in economics, definitely go for an economics or a commerce degree; if you’re interested in all three you’re better off doing an eco/arts double
there’s also not many job prospects for PPE in australia. if you’re interested in economics/business-related fields commerce and eco grads have a higher chance of grabbing those, if you’re interested in joining politics or public policy governance etc etc you’re better off doing a law / arts or a law / eco degree. philosophy just doesn’t have good job prospects all around