Answer
to show off, treat themselves simply because it is accessible to them
Step-by-step explanation:
Expensive people have a tendency to show off. Often times this is done for some sort of validation. This sort of need for validation can be a result of not having friends or real realtionships within their lives. By this I mean the geniune connections that humans form. It is possible they may have real relationships within their lives, but that is very rare considering the circumstances they live in. Having money opens up a new door of possibilities, which is why they can almost always get what they want. Money=accessibility (mostly commonly seen in material goods). They carry some sort of power because of this too, since it is evident that there are huge gaps within the wealth classes.