It looks like the 2009 IRC will be requiring residential fire sprinkler systems but the requirement won’t likely go into effect until 2011. This is one of the largest changes in the code for a long time that will dramatically affect life safety of homes. Jurisdictions such as Phoenix AZ have required residential sprinkler systems for a few years now. Since then there has not been a single death by fire in a sprinkler equipped home.
The typical sprinkler system will run as low as 80 cents per square foot to as much as $4 per square foot, depending on where you are located and access to water. A house using well water will likely need large reserve tanks to supply the necessary water flow. A house connected to City water may face higher fees to connect to the water system. So it will definitely cost more to have a safer home, but what is the price you can put on a life saved?