About $70 I think. I didn't have to deal with buying an extra battery, cause my original mower was stolen out of my garage. I keep the battery inside to prevent temperature degradation, so I still had it when I bought another mower with the battery included.
Before that I'd just mow half, and do other yardwork while the battery was charging.
I bought it after getting tired of having to fix my old gas mower. The pull cord broke, then the mechanism that it attaches to broke, then the priming bulb cracked and started leaking gas, having to go get gas for it, etc... the electric just works. I don't have to winterize or fuck with the carburetor, I just press the button and it works. It's more powerful than my old mower, doesn't bog down if I skip mowing for a week. It's better in every way.
We don't even issue alerts for anything below magnitude 5. Below 4 can barely be felt, we wouldn't even call that an earthquake here.