for single individuals to earn as much as (i assume US$) 150 a day means that the grid is horrendously unbalanced.

hell if I emptied my 30kw into the grid in my state/country at the most expensive time I'd earn AU$21.00

to earn US$150 means either HUGE battery capacity (and transmission capacity) or utterly rediculous power pricing... both mean really lousy power supply and grid design. I'm all for indipendance but the reality is we live in communities and count on the collective to rise us all up together.

that sort of profit is a clear warning sign of a broken community.

It depends a lot on the market, but before there were lots of batteries this was extremely typical in the Australian grid. You probably just weren't exposed to it as a consumer! Massive price fluctuations were the impetus for one of the first large scale grid batteries in Australia, and the batteries worked really well to solve it. It doesn't happen often, and nobody is getting paid $150 every day for their home battery. It's just for the extreme events.

As more and more batteries are deployed the price swings will decrease.

It's not a "broken community" it's just end consumers being able to help out in times of great grid need and getting compensated fairly for it.

California rate payers are being forced to essentially pay for fire insurance for CA residents who live in tinderbox areas, by way of PG&E rates, and burying lines that serve widely dispersed populations. That's the big difference. The vast majority of US residents have much lower utility rates.