Information doesn’t really change, in the sense that it is always valuable. Certain information is at different times more valuable than others, and the information itself changes but, as an abstract concept, information is always valuable—always has been and always will be.
Media change and sometimes a medium becomes very much less valuable and sometimes it disappears altogether. No one ‘writes in cuneiform on clay anymore. It is a cinch that all of those reference books that we have been using next to our desks or on top of our desks or next to our computers are going to be electronified or computerised, and they will go right inside the computers themselves.
The basic idea is that when media change but the data stays the same, you can buy the data for the new media at a much lower cost than it would take to control the data in the current media.