Well my contention was more with the "high return" and hard work being rewarded part. Something like 60% of US restaurants shutter within the first year. And 70% in 5. NYC is even worse with 80% closing within 3 years.
Not all of those that remain bring "high reward". Most of them are in the "some one's making a middle class income" bracket. So in terms of an investment restaurants are incredibly high risk for low to moderate return at best. And the ones that survive and succeed can't be the only ones where people are working their asses off, or the places where people are working hardest. Those numbers are just too high. There's very little way to guarantee or make your bar or restaurant successful.
Just as an example how rich did you're friends get? Cause noone's becoming a billionaire in the restaurant business (without founding a Starbucks or Chili's style chain).
In terms of how restaurants are as an investment its likely they would have come out much richer having simply dumped the same amount of money over that time span into simple investments like index funds. I know that largely wasn't your point, but I'm interested in countering this persistent idea that restaurants are money makers. I run into dozens of people a month who think restaurants are a safe or smart place to put their money. Or who think a restaurant is a sensible way to get out of the rat race. Take what you've earned, quit your job and live the high life in the restaurant business they say!
The thing to remember is that unless you are in the resto business currently, and plan to stay there forever. Never put money into a restaurant. Cause that money will be GONE.