I've only ever lived in high cost of living areas my entire life (SF bay area, and LA), grew up in an upper middle class family, and now have a household income in the aforementioned 5% range - well into 6 figures. We have a rather small mortgage for this area, and outside of a mortgage, have never had any debt (didn't have to take out any loans for school). So we run a steady surplus each month. However, I feel like our luck could change at any moment and we shouldn't take for granted our economic situation. It's not that I feel poor, but in no way do I feel secure. At any moment, the economy could tank, we could lose our jobs, etc, and I want to be in a solid position should that happen. This isn't to minimize the struggles of people who earn 30k and wonder where their groceries are going to come from next week - but rather to say that but for a bit of luck, I could easily be in that position as well, and could still end up there eventually.
As a result, we drive 15 year old cars, don't eat out, wear old clothes, are careful even about utility expenses (turn off lights, don't run the heater, capture water from the tap while waiting for hot water to come out), get groceries depending on what is on sale, etc. When we first got married, outside mortgage and property tax, we were probably living on $600/mo for two people. A lot of these are habits of people who grew up in poverty, but again, that does not reflect my background at all.
While not a majority, I feel there are others who are similarly situated, and feel the same. So while some may automatically think about people living beyond their means because they have achieved what to them seems like a "high" salary, this doesn't represent all the people who many might think of as objectively well off, but who absolutely do not feel that way.