If there is airspace where better than procedural standards can be used because you can now 'see' all the aircraft it will lead to significant savings, free up many flight levels, and routing restrictions etc.
These savings only occur if all aircraft are ADS-B equipped. 90% of my flying is under 10,000 ft. So, I am mixing with VFR aircraft which have no timeline for ADS-B and RA(Aus) aircraft which may have no transponder at all.
So, I am forced to pay for an upgrade that will give me zero benefit.
Australia is the only country in the world requiring all IFR GA aircraft to fit ADS-B.