Of course they're going to attack the 30% as too high. Obviously, their best outcome is reducing that percentage to zero. But to get there, their argument obvi

Of course they're going to attack the 30% as too high. Obviously, their best outcome is reducing that percentage to zero. But to get there, their argument obviously can't be "Apple is a monopoly allows it to extract 30%, which is too high, so we want it reduced to zero". That's not going to work. Rather, they get it to zero by saying "Apple is a monopoly and prevents competition by banning apps that implement their own payment processing system, so leave the 30% as-is but let any app implement its own payments". So the actual percentage, and the restriction against accepting payments outside Apple IAP, are two slightly different concerns. Reducing the percentage to 20% would obviously be a net financial win, but it's definitely not their main objective.