One Medical Group is a new model for primary care that aims to set a nationwide example. With 31 physicians in San Francisco and New York, it offers most of the same services provided by personalized "concierge" medical practices, but at a much lower price: $150 to $200 a year. One Medical Group doctors see at most 16 patients a day; the nationwide average for primary-care physicians is 25. They welcome e-mail communication with patients, for no extra charge. Same-day appointments are routine. And unlike most concierge practices, One Medical accepts a variety of insurance plans, including Medicare.