The fire extinguisher is not just for show
You are missing the point... no one ever claimed that hospitals weren't making money; however, emergency rooms, are not huge profit centers, at least compared to other departments. Some do lose money, but you're right, private insurance does pay off the losses sustained incurred by medicare, medicaid and underinsuredOff-site part of the hospital system, and yes they are all placed in "strategic areas" (i.e. not ghetto).
As to the ER being a loss leader, it's still a part of the package. How many of those mega-bux cash cow inpatients made entry to that hospital through the ER.. I'm guessing that they, plus the price gouging that occurs to those who are in the ER with insurance generate than enough cash to offset the non-payers down there..
Then there's the grant funding they get