permanent business boost / well rewarded

That was not claimed by the author.

For better or worse, gasoline tends to be break-even for stations - from the operators I've talked to, maybe they make 5 to 10 cents per gallon. They make most of their profit from the shop. A month's worth of gasoline sales might not cover the upkeep and depreciation of the generator.

I'm more curious to know if any other stations installed generators after this experience. I wouldn't be surprised if the answer was "no".

And how frequently do power outages of this length happen in a given city? Considering none of the other gas stations had infrastructure in place to handle this event, I would assume it's the first time in decades, or ever.

To be fair, being able to increase your prices would have those same downsides too. It sounds like this kind of emergency preparation would have to be publicly subsidized for it to be a common thing.