If you are going after full profit optimization we are leaving huge amount on the table by offering billionaires food at prices that are insignificant for tem. Maybe we should start optimizing for the million dollar burgers then?
If the average Brit is spending %10 of their daily income for a meal, obviously its suboptimal for a person making a million a day to eat anything for less than 100K. In fact, it doesn't even have to have anything to do with percentages, maybe the meal can be optimized up until 999910GBP. Even the rich guy needs to eat, optimize the prices to the point that he has to choose between starvation and 999910GBP burger