One of the major benefits of SBAS is the improved availability of the GPS signal, so an alternate is not required when your destination is only served by a GNSS approach. I would have thought that this is more important (cost-saving) to Australian pilots than the use of lower approach minima, given our weather conditions most of the time. It will be even more important when Airservices gets around to de-commissioning many of the local NDBs.
But this is likely to be addressed by receivers simultaneously using Galileo and GPS Block III signals within the next ten years. (More satellites to choose from, and receiving on two or three frequencies simultaneously.) So as a tax payer I'd question the wisdom of developing a network of SBAS reference stations at this stage.