Law of supply: the price of a product and its quanitity supplied are positively-related*. The higher the price, the more incentive people have to offer a product for sale. HT Glenn Reynolds
As King recently noted, it's easy to hold some factors constant when building economic models. So in a theoretical world, it is relatively easy to hold, say, health care quality constant when wondering how minimizing health care costs (macroecnomically) would affect things. In the real world... not so much. But maybe Obama really wants to force people into dentistry.
*Backwards-bending individual labor supply curve noted.