What's the controversy over whether these types of good exist? Is it over whether the family would truly choose to buy more staple food and less luxury food ba

What's the controversy over whether these types of good exist? Is it over whether the family would truly choose to buy more staple food and less luxury food based solely on cost and not some other figure of merit such as nutrition? For example, I could see a situation where a family might still choose to purchase luxuries in the event the staples went up in price in order to maintain the wider variety of nutrients they would get from the varied diet than what they would get from eating just the staple. Obviously there is some limit to this, where the need for simple calories outweighs the need for a wide variety of nutrients, at least over short periods.