I have no right to make a value judgement on how Joe spends his money in this example. However that is what the study asked participants to do. claiming that people scrutinized low income families based on that part of the study is incorrect. They simply tended to look differently on a spending decision to buy a luxury item based on income. Something the study required them to do.
That said if a friend asked me for on advice on how to spend $200 my answer would depend on their financial position. If they had plenty to spend it doesn't really matter how they spend it. If they have very little I might recommend they spend it on a necessity rather than a luxury. That is not a judgement. It is simply the wiser choice. I suspect this could have been why people answered the way they did.