“at the expense of” in “But the problem with entitlement is that it makes people need to feel good about themselves all the time, even at the expense of those around them.” 是什么意思？

It means entitled people will make other people feel bad, lose out, get upset etc. if they have to in order to get what they believe they deserve. “I will become extremely rich, even at the expense of my relationships with my family and friends.” For example this means “I will sacrifice a good relationship with my family and friends if it means I can get rich.”