This was based on a question that my economics professor in college had asked us. His question was more to the effect of “What’s a good/service people buy when they have a bit of money, then they stop buying or buy less of it when they get some more money, and then they start buying it again once they have even more money?” — feel free to answer that too.

My first thought was alcohol: lower class people might buy more of it to cope with their difficult situation, whereas upper class people have more money to spend on vices and luxuries such as alcohol. Not sure if this theory holds true.

The best answer I’ve been able to come up with is golf carts, at least in the US. It’s common to see lower class people drive golf carts around their trailer parks or neighborhoods, whereas middle class people rarely do that. An upper class person might live in a wealthy neighborhood with its own built-in golf course, or the person might even own their own golf course(s).

Some dubious investments, such as crypto or donations to certain social organizations or politicians might also qualify?