There are a limited number of grid topologies where a battery can add this kind of value. It's really unusual to be this extreme.

Correct, at the current price.

I saw elsewhere that battery price is going down 15% per year. So, over time, more grid topologies will be able to leverage this technology.

All grid topologies. Grids will be rendered obsolete absent forced support.

I think part of the savings don't go directly to the battery owner, but instead prevent the electricity suppliers from price gouging the customer.

Happens a lot with renewables. You personally don't capture all the value you provide. This is part of the reason that rooftop solar should get paid more than the going rate but even 1:1 rates get attacked as some kind of scam, even as they reduce peak load which may be literally 1000x more expensive than average.

Correct. A proper grid system would pay a premium for the size of the solar grid that fulfills solar-induced demands.

After that, solar should get paid grid rate.

I have no idea if anyone has bothered to calculate what the solar-induced demand is.

Unfortunately, they don't really reduce peak load anymore. With the solar-adjusted demand curve looking duck-shaped, the peak load is now in the late-afternoon/early evening

I'm in Australia and we recently committed to putting solar panels on the roof of our small office building. Pay-off projection in the estimate/quote was all of 2 years!

Nice! I had my solar panel installed on the roof of my house in 2015, and they have a pay-off projection of just over seven years. At the beginning of the year, my neighbor had solar panels installed, and we calculated his pay-off projection of just over four years (both of us took advantage of available subsidies).

And battery storage is only getting cheap, I believe at a rate of roughly 15-20% per year.

Yet we also hear that battery production is a bottleneck and the reason why automakers other than Tesla are so limited in their EV offerings.

Other automakers are limited in their offerings because they didn't commit with any enthusiasm until a few years ago, and the development time for a new car is at least that long. There are a whole bunch of new EV options coming to market in the next year or so.