Every one has a definition of what luxury actual mean to them, the "poor" from the picture you sent obviously see dressing as a way to showcase luxury to him, but the "rich" might have a different area he expresses his own display, might be houses, cars etc, you can't place a particular standard to luxury.
That poor guy night not even be coming from a decent home, he has dressing might have dressing as a priority, can still be a misplaced priority from his end which can contribute to why he is poor.
If we look at luxury from every assumption, of course there will always be a difference between the assumptions held by poor people and the assumptions held by rich people. Because people who are considered rich by many people around them will always be considered good for what they wear, while people who are still considered poor by the people around them will always be considered useless for what they wear even though they do wear expensive clothes on their bodies. I actually don't consider rich people based on the clothes they wear, because for me people who have more assets such as houses, cars and land are the real rich people even though they still wear simple clothes on their own.
There will always be many definitions of wealth and poverty in the view of every human being, but it seems that the OP refers to the use of money to judge who is rich and who is poor, but it is a little unclear that most rich people actually prefer simple clothes rather than looking much more attractive with luxurious items, but not a few rich people also use expensive items on their bodies, and I think we cannot see what the rich can and cannot do in the use of their money.
But I always believe that rich people use their money more for their needs rather than just for style like poor people in general who want to look rich.