Simply put, poor people buy for style and cool while rich people buy for quality, utility and prestige.
This goes back to how to treat money in life, in the sense that poor people are not not allowed to buy expensive goods and indulge in what the rich do, only they do not have enough to live much longer but they force it to fulfill their desires not their needs.
Yes the way money is spent by the classes and category of people can't be measured overtime but this happens this way because people try to suit in with their preference of their demands and they can't do more than that, the rich can spend on luxury and quality stuff cause they can afford it and the poor in the other hand will always go for what they can afford in a low quality and thus is the distinctive difference between both the rich and the poor.