Hurricane Ian survivor from Fort Myers Beach here.
I've been through numerous hurricanes before, but this one was different. Our building was designed to take on a storm like this, and it performed better than the engineers thought it would, but we still got nailed. We had multiple large automatic generators which power the entire place, even the fountains and landscape lighting...all of them were damaged beyond repair. The electrical distribution boards got wet with salt water, water pumps and other infrastructure did as well. Still no ETA on when I can move back home again. About half of my coworkers who live on the mainland also lost their homes.
So...I've had a lot of practice with emergency lighting over the past few months. While I have all sorts of fun flashlights, the real workhorses of the show have been the Duracell lanterns from Costco. Both the 4D & 8D models (NOT the Hybrid models, as those have a terrible CRI, terrible color temperature). Also, the Mr. Beams MB530 lights.
The MB530 are motion lights, but they put out a dim glow when it's dark and go to full brightness when they see motion. We had these all over the place even before the storm. In normal times, I'd go 1-2 years between battery changes on these. With the generators knocked out, these came in handy for times when we didn't have the lanterns going. When it's pitch black, their dim glow lights up the room well enough to see where everything is. The bright light activated by motion is very bright, and useful to locate one of the lanterns.
I don't know that there's a cheaper way to do emergency lighting than this. The Duracell lanterns are sold in pairs at Costco for $19-$25, so $9.5-$12.5 each for the lanterns. D-Cell batteries are $1.15/each at Sam's/Costco, so $4.60 in batteries for the lantern. They say these will last for 60 hours at 250 lumens, or 240 hours at 65 lumens. $4.60/60hrs=$0.076/hr, $4.60/240hrs=$0.019/hr. Certainly not as cheap as regular lamps on grid power, but hardly burdensome, for a very low up-front cost.