Since I do not inject Sculptra, I will leave the cost consideration replies to my colleagues.
I would like to address your last paragraph which particularly galls me.
It is true that dermatology residencies have been the hardest ones to obtain for at least the past fifteen years. However, not due to what you perceive as unfathomable riches. In fact, there are many specialties whose average physician makes far more money than the average dermatologist (Speaking of salaries are you as irked by how much our sport "heroes" make. Gilbert Arenas, a basketball player, makes nearly as much money for playing ONE game as I make in a year. And Gilbert is no Tiger Woods!).
Most prospective dermatologists enter the field because it is the only area which covers nearly the whole panoply of medicine. No other specialty provides the variety to include surgery, medicine (and nearly all its subspecialties such as endocrinology, rheumatology, internal disease), pathology, pediatrics, geriatrics, allergy, vascular disease, genetics, gynecology etc. Plus, as you have noted there is the cosmetic aspect. I am sure you can acknowledge that my specialty has been at the forefront in this area (lasers, chemical peels, dermabrasion, Botox, fillers, hair transplants, tumescent liposuction etc.).
The skin is a fascinating organ with its glandular structures, cellular proliferation, neuro-endocrine, receptors; the science of it is of unending appeal.
It is a joyous specialty and most polls show dermatologists to be the happiest in their field. Incidentally, physicians are a greatly demoralized group; polls show the satisfaction rating has dropped from 95% when I began practice to less than 50% today. Government interference with its CLIA, HIPAA, I Pledge, malpractice, HMO's, shrinking reimbursements, more demanding patients, and prospects do not look good).
Every day the average dermatologists sees a number of interesting, challenging cases (besides the humdrum). Eg: today I saw a patient who had seen his family physician, an orthopedic surgeon and a hand surgeon due to a trigger finger, and carpel tunnel syndrome. Finally, he ended up with a rheumatologist who referred him to dermatology (a retired colleague). On presentation he had a number of small papules in his arm pits (Praise the Lord he did not end up in a mall spa which you seem to regard as some sort of cosmetic savior. His small bumps would have ended up in the trash.) It turns out he had papular amyloidosis (a type of protein which can deposit in the skin). Further work up led to the diagnosis of multiple myeloma, a cancer of the plasma cell. He is doing very well with chemo.
Also today a young lady with Darier's Disease (genetic disorder of faulty keratin formation) is flaring badly and has not responded to the usual treatment. We may try Photodynamic therapy (PDT) or Botox each of which have been used, but studies are very limited. Will be interesting to see if they give her surcease.
The point is every day presents its challenges and fascinating cases.
Since I am sounding in parts like I am answering an essay for a residency application (Why do You Want to Become a Dermatologist?), I will speak to the other fallacious comment. That somehow society will be better served if entrepreneurs and giant corporations are allowed to deliver what you perceive to be better and cheaper care. It is true that the care will be cheaper (with its fake Botox and fillers, cheaper machines) but I can assure you no better. Where the only motive is profit, patients should beware.
I am sure I am not alone among physicians on this site in seeing an increasing number of botched procedures, missed diagnoses, and shoddy medical practice by people who have no right practicing medicine. In fact many are practicing medicine without a license. Many of these medi spas would have already been shut down if the medical boards were adequately staffed. Time was when I would see spa induced problem problem every few months, now I see them about every other week. Not necessarily harming patients (although I have seen three laser burns, scarring from a poorly applied peel, a generalized herpetic infection and a bacterial infection), but needlessly expensive treatments (laser for psoriasis without trying even topicals): freezing and lasering granuloma annulare, repeated useless peels for syringomas, etc.,
Entrepreneurs and CEO's have a different set of ethics. Believe me, they will hire the token physician who is willing to sell out his license (I will be kind here) allowing himself to be the "medical director "and permitting lay people to practice on the unwary patient who has stumbled in after succumbing to the ads of the shallow but slick PR people. If somehow you think you will see less rather than more granulomas from Sculptra when these poorly trained people are let loose you have another think coming. .
I personally believe events will be going in the other direction. More supervision. More restrictions. The general public after hearing stories of woe and experiencing mall cosmetic medicine, will demand more supervision of these places not less.