In addition, salary figures often understate physician earning power since they often do not include revenue from business activities: fees for blood or pathology tests at a lab that the doctor owns or “facility” charges at an ambulatory surgery center where the physician is an investor, for example.

“The high earning in many fields relates mostly to how well they’ve managed to monetize treatment — if you freeze off 18 lesions and bill separately for surgery for each, it can be very lucrative,” said Dr. Steven Schroeder, a professor at the University of California and the chairman of the National Commission on Physician Payment Reform, an initiative funded in part by the Robert Wood Johnson Foundation.

Doctors’ charges — and the incentives they reflect — are a major factor in the nation’s $2.7 trillion medical bill. Payments to doctors in the United States, who make far more than their counterparts in other developed countries, account for 20 percent of American health care expenses, second only to hospital costs.

Specialists earn an average of two and often four times as much as primary care physicians in the United States, a differential that far surpasses that in all other developed countries, according to Miriam Laugesen, a professor at Columbia University’s Mailman School of Public Health. That earnings gap has deleterious effects: Only an estimated 25 percent of new physicians end up in primary care, at the very time that health policy experts say front-line doctors are badly needed, according to Dr. Christine Sinsky, an Iowa internist who studies physician satisfaction. In fact, many pediatricians and general doctors in private practice say they are struggling to survive.

Studies show that more specialists mean more tests and more expensive care. “It may be better to wait and see, but waiting doesn’t make you money,” said Jean Mitchell, a professor of health economics at Georgetown University. “It’s ‘Let me do a little snip of tissue’ and then they get professional, lab and facility fees. Each patient is like an ATM machine.”

For example, the procedure performed on Ms. Little, called Mohs surgery, involves slicing off a skin cancer in layers under local anesthesia, with microscopic pathology performed between each “stage” until the growth has been removed. While it offers clear advantages in certain cases, it is more expensive than simply cutting or freezing off a lesion. (Hospitals seeking to hire a staff dermatologist for Mohs surgery had to offer an average of $586,083 in 2010, even more than for a cardiac surgeon, according to Becker’s Hospital Review.)

Use of the surgery has skyrocketed in the United States — over 400 percent in a little over a decade — to the point that last summer Medicare put it at the top of its “potentially misvalued” list of overused or overpriced procedures. Even the American Academy of Dermatology agrees that the surgery is sometimes used inappropriately. Dr. Brett Coldiron, president-elect of the academy, defended skin doctors as “very cost-efficient” specialists who deal in thousands of diagnoses and called Mohs “a wonderful tool.” He said that his specialty was being unfairly targeted by insurers because of general frustration with medical prices. “Health care reform is a subsidized buffet and if it’s too expensive, you go to the kitchen and shoot one of the cooks,” he said. “Now they’re shooting dermatologists.”