Im not sure "riding an expensive car" is a good way of measuring the effect of income. Could be many reasons why having an expensive car would make you a worse driver than just income.
For example:
-if you want to show off with your car, you buy a flashy expensive car. If you want to show off with your car, you're gonna drive too fast.
-expensive cars may give a sense of security. You tend to underestimate your speed when driving an expensive car. In contrast, when speeding in a cheap car, the whole thing seems to fall apart around you.
U.S. surveys find that the rich give a smaller percentage of their income to charity than do the poor.
Imo its hard to conclude from this that rich people are less generous. They give a smaller percentage of their income, but they give more in absolute numbers. Its not obvious which measure is appropriate to measure generousity.
"Our findings suggest that if the pursuit of self-interest goes unchecked, it may result in a vicious cycle: self-interest leads people to behave unethically, which raises their status, which leads to more unethical behavior and inequality."
I don't believe the causality is necesarily in the way this researchers describes.
Maybe being selfish makes you rich, maybe being rich makes you selfish, maybe both. Maybe there is something else going on.