Typically staffed by nurse practitioners, walk-in clinics are aimed at treating minor ailments such as strep throat or ear infections. They offer weekend and evening hours for people who can't take off work during the day or face long waits for appointments with their regular doctors.

Retail clinics began popping up across the country in 2000 and now number roughly 1,200, according to RAND Corp., a nonprofit research group.

The benefit of these walk-in clinics, however, depends on a consumer's situation. Because they are significantly cheaper, retail clinics often appeal to people who are uninsured and have to pay out of pocket, said RAND researcher Ateev Mehrotra.

The cost of care at walk-in clinics at stores such as CVS, Walgreens, Target and Wal-Mart is on average 30 to 40 percent lower than at a physician office or urgent care center and roughly 80 percent lower than an emergency room, a RAND study shows. For consumers, the average cost of an ER visit for strep throat can be $550 to $750 vs. $59 at a retail clinic, data from insurance giant Aetna shows.

Patients "really like the predictability of the cost," Mehrotra said.

Cost also is playing a larger role in people's decisions on where to get care as high-deductible insurance plans that require consumers to pay more out of pocket grow increasingly popular, said David Van Houtte. The Aetna senior network manager negotiates contracts with retail clinics nationwide.

For people with insurance, who would have the same co-pay as if they went to a doctor's office, retail clinics are more about the convenience, Mehrotra said. Getting time off from work can be a struggle for many people, he added.

Sujal Patel stopped by a MinuteClinic inside an Atlanta neighborhood CVS on a recent afternoon after battling a nagging sore throat for three days.

"If I had gone to a doctor, I would have had to take time off," he said. "Doctors don't usually see you right away."

At the CVS clinic, he was able right away to get medicine for his respiratory infection and to help him sleep, without having to drive to a separate pharmacy.

Retail clinics might be one solution to help curb the nation's increasing health care costs, although they aren't a magic bullet, Mehrotra said. About 17 percent of visits to ERs could be treated at a retail clinic or urgent-care center -- saving up to $4.4 billion annually, according to one RAND study.

"No one should think this is really going to solve the cost spending trends in the United States -- though some would argue every little bit helps," he said.