I think there is no definite answer to these questions. There's no answer applicable to everyone. Each person's decision for each surgery is different. But that's why I agree with the people in class who said patients need to undergo psychiatric evaluation before they receive a cosmetic procedure, because I think the point at which plastic surgery is harmful is when it becomes a compulsion or obsession to look a specific way.
If a psychiatrist examines a patient prior to a cosmetic procedure, they might be able to reveal the reason for wanting such a procedure done. Most people are insecure about some form of their body, and having a desire to change that isn't necessarily a pathology. Wanting to change just one aspect like ears, wrinkles, or breast size might be perfectly fine. The patient recognizes an aspect of their life that doesn't make them happy so they seek ways to correct that. In the same way people may quit their job to find something else that makes them happy, people may have just a few cosmetic procedures performed to increase the quality of their lives. But I think that the point this mentality turns into a real psychiatric concern is when they grow to hate something about themselves. Dissatisfaction about wrinkles is one thing, but real hatred about having them is completely different. When you hate a part of your natural body, I truly believe there is a deep rooted issue within yourself that will not be cured by just a few cosmetic surgeries. No amount of surgery will ever be enough to overcome all the flaws you see in yourself. There will always be something wrong that you become obsessed with correcting. I think it is the people who experience hatred about their appearance that become obsessed and compulsive with cosmetic surgery.
In the national geographic clip, Steve Earhart was in the process of having his 54th procedure scheduled. This one was to remove a small amount of excess skin above his eyes. He disliked that it made him look old. Looking at that procedure by itself, that would be completely normal and would probably pass a psychiatric evaluation. But coupling this procedure with the other previous 53, Earhart seems completely obsessed with looking young. No matter how many procedures he got done, time always kept aging him. He wouldn't even tell people how old he is. It's as if he's ashamed of his age. He never actually used the word "hate" in this clip, but a psychiatric evaluation might reveal why he cannot bear to look "old."
Side note: I hold doctors responsible for making sure their patients are in a sound state of mind before performing cosmetic procedures. A psychiatric evaluation would fulfil this, but for now there is nothing stopping doctors from performing these procedures on whoever has the money. A physician's oath is to hold the health of the patient in the highest regard. But many in fields such as plastic surgery become more concerned with their income than the mental or physical health of the patient. In the Swan clip, the doctors are blatantly convincing their patients that they need these unnecessary procedures for their potential to be "fulfilled." To me, that is beyond abhorrent because they are using their position of expertise to manipulate the susceptible. A physician should be concerned with the patient's mental and physical health, not their bank account.