Essentially, such a person is saying; “I am either extraordinarily ignorant, or just plain selfish. If I were not ignorant, I would know that children are dying from diarrhea or malaria, because they lack safe drinking water, or mosquito nets, and obviously what I have spent on this watch or handbag would have been enough to help several of them survive; but I care so little about them that I would rather spend my money on something that I wear for ostentation alone.”
Within the article he mentions an interesting point from a 19th century philospher that noted that as social status becomes more and more tied to wealth, as opposed to say wisdom, knowledge, skill, or moral integrity, then the rich will pursue expenditures that serve no purpose other than to display that wealth. These kinds of purchases should be ridiculed on the above grounds.
Just to briefly note, this does not apply to something like the purchase of an RV or nice car. These are useful and the premium you pay is providing you a real functional enjoyment. We're talking here about purchases that are exclusively for the display of wealth. He uses the example of a watch that's actually not as good at keeping time as a cheaper alternative.