Size of Files, Size of Library
It's not the size of your "iTunes Media" files that best describes how big your media file collection is. Often, querying Correspondents will report that their iTunes Media folder is so many GBs (or so many days-worth). But if that total includes a lot of video then the number of files is smaller than the same-sized folder containing just 128kbps audio files (eg: my "Star Trek" with Extras at 6GB+ is a little smaller than my "Compilations" folder which contains over a thousand files). Very few of my scripts and apps directly work on the files in the iTunes Media folder anyway, so in many cases its size is irrelevant; scripts work with tracks in iTunes, so the number of tracks is more important than the size of their files. A better relative measurement for comparison purposes is the size of your "iTunes Music Library.xml" file (located in ~/Music/iTunes). It has an entry for each track in your library and all (well, most) playlists. Therefore, the more tracks and playlists you have the larger the XML file will be.