Fast food price index across the US

The price range across Taco Bell's taco is interesting.

I've always wondered how their business can be profitable, but I have to remind myself not everyone only shops on the dollar menu. When the mexican pizza is around ~$8, I can see how they could have quite large margins.

But, on the value menu stuff, I really wonder if they make any money at all on them after labor + ingredients + operating costs.