There are costs to have the aircraft on stand by each day (sitting around) - then costs to operate. Just in Victoria, the cost is north of $20m, and operating costs north of $15m each fire season. So ~$30-40m PA spent. A lot of cash for not a lot of return.
To quote one politician;
"What is the cost of doing nothing?"
So $30-40m that may reduce the severity or prevent fires is a small price to pay.
If the States, or the Commonwealth, were to purchase the CL515, they are multi-role aircraft and could carry out SAR operations. At present we do not have an aircraft within our SAR capabilities of landing on water for rescue purposes.
CL-515