Do batteries really make sense if you look at total system cost? You still need peaker plants to power the country if there are longer Dunkelflauten. I am skep

Do batteries really make sense if you look at total system cost? You still need peaker plants to power the country if there are longer Dunkelflauten. I am skeptical that the total cost for m hours additional power need: n hours battery power + (m - n) hours of peaker plants is going to be cheaper than m hours peaker plant power.