While I'm not arguing against spending money on other needy aviation causes SBAS should have been implemented a long long time ago. It's not just aviation that benefits in fact the big benefits to aviation are small compared to the benefits other industries gain from SBAS.
The safety benefits it brings to aviation are significant, particularly by enabling 3D approaches at any airport that can support an RNAV approach.
No doubt some will ague BaroVNAV does the same thing. Yes it does, provided the correct Baro setting is set. There's plenty of opportunity for the wrong Baro setting to be set and it happens. SBAS avoids these errors.