They are for sure the weak link. It's definitely coming down in price. Hopefully lifespan will go up as well. I wasn't super impressed with the power banks, and I think the solar roofs are a total waste of money. The guy is a genius, but not every idea is a good one. Electric vehicles will just about take over in the next 5-10 years, and that will make all the difference in the world of batteries.
I could seriously power several houses here with 7 kW. Of course no such thing as electric stoves in these parts. And of course no one has a dryer either.