> It is hard to beat the economies of scale of a restaurant, as much as the "you only need to factor the cost of raw food" camp like to tell otherwise. From a purely economic perspective, a kitchen at home, when other sources of food are widely available, is tough to justify.
It really depends what one eats. If one is okay with eating widely available low cost foods, then yes, commercial kitchens are more efficient. For example, Burger King here will sell you a three whopper, three cheeseburger, and three fries family meal for $14.99 (silicon valley prices, likely lower in the rest of the nation). Pretty hard to compete against that if one considers the cost of making a burger from scratch and cleaning up the mess from deep frying at home.
But fast food is a low margin high volume business. Looking at higher margin items, like what you'd eat in a steakhouse, the economics of a kitchen change dramatically. For example, I recently bought four USDA prime tenderloins from Costco for roughly $58 total. Each one of them, plated and served, would be $35 to $50, excluding taxes and tip. Given that cooking those is pretty easy (either with just an inexpensive cast iron pan and oven, or using sous vide if one wants to get fancy) and takes a grand total of five to ten minutes to make, then the kitchen becomes a much better value proposition.
And that's saying nothing of people with restrictive diets, where oftentimes it's just easier to cook at home. Depending on which friend I'm dining with, the restrictions might be celiac (strict no gluten, not fad diet no gluten), low/no carb, pescatarian, vegan, religious dietary restrictions, nut allergies, and so on. Sometimes the combinations basically exclude most of the restaurants out there, and at that point, it's easier to cook at home than go out only to be restricted to a few items in the menu.