It seems like an unreservedly good thing if people with home batteries can help prevent brownouts and reduce prices for everyone else. Also, I believe the $150/day figure was during a rare heatwave event when prices had surged to 100x their typical value ($5/kWh). It’s like any other investment where you outlay cash upfront and hope to make it back over time, whether via reduced costs for your own electricity usage or selling it back to the grid when doing so is profitable.