Poor buying when things expensive they are expert buying top in everything and FOMO in also the middle class are expert on buying highest prices and not just buying they buy it with credit.
Rich buys when something is with good price low price poor buys just to spend money.
Middle class behave like poor too they buying expensive.
A poor man buys things in most cases to please others, they many not necessarily need that item or commodity, for example you will see a young guy who do not have any investments, he is not even sure of what he will eat tomorrow but when he cashes out the very first thing on his mind is to buy an iPhone. This is not the mentality of a rich man, a rich man buys things out of need and not out of want, meaning that they focus on things that are more important.