ACA and Exchanges Lower Costs?

The idea that the ACA or the Exchanges is going to somehow magically reduce the cost of care is fantasy. What happens when you flood the system with a couple of million Californian's that were previously uninsured, many of them with chronic untreated conditions? It seems to be to be the simple economic premise of "supply and demand". Not to mention that the penalty for not signing up in 2014 is almost nil. Love to hear people's thoughts about this...