Freestanding emergency departments started as a way to serve rural areas, bringing some hospital-level services to communities that didn’t have them. But they only started to rise about a decade ago, growing to at least 222 facilities across 16 states, as hospitals build stand-alone emergency rooms that can treat a wide variety of medical conditions.

The Seattle Times’s Carol Ostrom had an important story Sunday that gets at why this could become problematic: Emergency rooms tend to have higher costs than other doctor’s offices, or even urgent care centers. “The ER reimbursement for a sprained ankle might be $700, three or four times that for a visit in a primary-care or urgent-care clinic,” an executive with Regence BlueShield tells her. “For hospitals, he says, ‘it’s a bonanza.’” Seattle, hardly a rural area, currently has three free-standing emergency rooms under construction. One that just opened an hour north of the city has more square footage than an NFL football field.

Hospitals, however, say there is a place for these clinics, which can deliver more comprehensive care than the standard doctor’s office. They have a decent case to make for why free-standing emergency rooms have a place in the American health care system. The number of non-rural emergency rooms has decreased by 27 percent over the past two decades, according to a recent Journal of American Medicine Association study. Freestanding emergency departments could fill that space.

Whether that space actually needs filling, however, is questionable. About half of the medical cases that hospitals see are either “urgent” or “semi-urgent,” suggesting they could be seen elsewhere at a lower cost. While an increase in freestanding emergency rooms has the potential to bring better medical services to underserved areas, a building boom in a major urban area like Seattle likely does not bode well for the prospect of controlling health care costs.