What no one is telling you is that the actual published fare tariffs don't change that often. What does change and is dynamically managed by the airlines revenue management departments is the availability of different fare classes that the tariffs book into. It's the combination of fares and fare class availability that determine the current fares available for a flight (and not just the lowest fare).

On ExpertFlyer, we show all of this hidden raw information that normally only travel agents have been able to see as we buy the data from the airline reservation systems. The first few pages of our education guide give a simple overview of how this works: http://www.expertflyer.com/edu-guide.pdf