This does bring the question up in my mind of what a restaurant that wasn’t a luxury would look like, ie, something that sells ready to eat food at prices that make it competitive with cooking at home, and which is healthy enough to eat on a daily basis without ill effect. My guess is that it would be largely a matter of having to carefully choose recipes that both use ingredients that are cheap in bulk, and able to be at least partially automated to keep staff costs low, but which are still nutritious and rely on minimal processed ingredients. Probably soups and chili and the like I’d imagine.