Some experts say high costs for patients at big-city hospitals reflect a free-spending, out-of-control medical marketplace. Others say medical costs are higher in urban areas because the poor need more care and the rich demand it. Others say the profit motive is at play. Still others say that when lives are at stake, cost should not be an issue. Whatever the reason, the question itself has taken on added importance as the Obama administration pushes a massive expansion of medical care to the uninsured.