Earlier quoted context omitted.
Or, who's going to pay $15 or $20 for a sandwich? Most people will pass.
Why will they pass? What's the calculus? "I could make it myself for less" ? "It used to be less" ? "It shouldn't cost that much " ? Isn't it more likely to be true that they will pass because they've become accustomed to crazy low prizes for prepared foods?
If another restaurant can make a profit by increasing efficiency and keep prices low, they win over one that doesn't. And restaurants have no real business moat - recipes for most things are known, and it's mighty hard to invent something totally new.
Let's imagine that all restaurants raise their prices like the article claims. Suddenly, the margins at 19%. Let's also assume that consumers are willing to pay, but if they find something of similar quality but cheaper, the will move. Then one self-interested restaurant owner could simply lower their price by a bit, and they will make more money than their competition.
And so all restaurants have to do the same. So the margin of 5-9% is what you end up with.
TBH, as an investor, if you're given a 9% return on investment, i think they would be ok. It's not great, but it's not the worst. 19% margin is too high: most junk bonds are returning something like 8-10% (sure some are like 20%). Is running a restaurant riskier than junk bonds?