The ambulance is not a free service in Victoria. Check that your private health insurance, travel insurance or that your home state has reciprocal agreement. 

For Victorian residents, the annual subscription is not that expensive and covers you for the whole year, not just this race. The cost of a ride out of there in a helicopter would be very expensive.

Pics and video below are from during the 2015 TNF100 in the Blue Mountains. Really experienced runner slipped and had to be choppered out. It can happen to anyone of us.

Heli evac from race in Blue Mountains