Aside, I think a big battery in Australia makes a lot of sense because they have lots of sun year round and lots of unused space. So you are pretty much just storing for night time and can easily build solar panels.
In many other places, you have to store for much longer term which means you need much bigger batteries (and bigger generating plants).
This is to say I think the cost in a place like Australia may be 100s of times less than places in most of the USA (which is where I live).
Yeah, that doesn't make sense. Overbuild and interconnect rather.
You can't do things like store summer solar energy for the winter. But there are plenty of places in the US where the sun is nearly always shining. If you can share that energy across the county you're in good shape. Likewise with the wind.
Again it helps you have solid baseload power. It's just nuclear is so expensive and takes so long to build that you can build twice the capacity in solar and wind plus a battery, plus a gas plant for a backup in less time and for a similar price.