This project is about expanding the output of the Snowy Mountains scheme, which means greater demand on the storage capacity, not forgetting 1000km of transmission lines to get the energy to Adelaide which means the grid components that failed them last time are in exactly the same place.
The proposed expansion is $1/W capacity.
The expected price for the Neoen project is in the order of $1/W ($100M for 100MW output, 129MWh capacity)
Note that the actual price on the SA battery is not known, and there has not even been a tender out for the Snowy expansion much less accompany at work digging tunnels suddenly finding that Australian conditions are breaking their equipment more than expected :)
The expected cost overruns on the SA tender are aporoximately zero, the expected cost overruns on a large hydro project between initial estimates and completion are approximately 100% based on industry standards.
The Cultana proposal was A$500 million for 300 MW, which is more expensive per Watt but not several times. No way they could build it in 100 days though.
