This is too shallow of analysis to draw this sort of conclusion....

This is too shallow of analysis to draw this sort of conclusion. Great, Kidston does 250MW over an hour and can do this for 8 hours. Eraring does 10x this per hour and also during low demand times. Over the last year, Eraring has averaged ~42000MW/day. Going to need a fair few of these hydro batteries to keep up. Demand is ever growing for so many reasons. The electricity market will grow rapidly volatile once stable producers (coal) are removed. QPME and electricity prices are in no way "numbered" - you need to dig deeper than this.