I went to a private school where a lot of the people there were spoiled brats.
IMHO several of them had some borderline traits, and had some of the elements of that disorder. It was a product of having rich parents who spent hardly any time with their children, and then dumped them in a private school for most of the year. Some of these children were then shipped off to private summer schools or camps for the summer. I knew a few that only saw their parents about 3 weeks out of the entire year.
Several of these people ended up having cluster B traits, but they did not have enough criteria for borderline PD. They had a healthy amount of narcicism, and many could not continue the family status because they didn't have the mental discipline to continue to run the family fortune. Others, well they inherited mommy and daddy's business, but the business was to the degree where it was now idiot-proof. E.g. one guy I knew, his dad owned a private college. He took it over. All he had to do was sit in meeting and nod his head. He didn't know WTF he was doing other than earning a few million a year.
Others I've seen who are successful are so because they are hard working, and they want quick results. They are sometimes inpatient.
All in all, working with people in a high SES can present with different but even more frustrating challenges than those in a low SES.
One of the patient's I had who came from a wealthy family, the mother was homemaker and spent every free moment researching the disorder. She had a feeling that if she spent enough time, she could cure her son. She tried to have me do a number of ridiculous things such as entertain the notion that his schizophrenia was caused by a caffiene allergy. (He drank about 3 cokes a day, no signs or allergy whatsoever). Every single quack idea she got from the internet, she tried to have me investigate it, wanting me to spend about 10 hrs a week on each of these quack theories.
As much as I sympathised with her situation (hey, if my kid had a bad case of Clozaril-resistant schizophrenia, I'd probably be as bad), the case was ticking the heck out of me.
but are high functioning so they don't actually have any disorder.
They may indeed have the disorder, or enough to meet a personality DO NOS dx. Many wealthy people I've known have dysfunctional family structures. There's a mix of narcissism, entitlement, borderline PD among other issues.
But since they are wealthy, they can get away with it. They can afford to maintain their dysfunction. Can't get the kids to clean up their rooms? The maid will do it. Can't discipline the children? Send them off to private school. Problem with the wife? Get a mistress. In some of these cases--they'll get a boutique doctor to prescribe them Xanax.
They certainly IMHO would meet enough to be diagnosed, but since they don't have to see a mental health professional anyways, their money buffering them from needing or wanting extra help, they don't get a diagnosis.