Guess I shouldn't worry so much...
FS9 is at 21.1 Gb
FSX is at 65.4 Gb
I try to control sizes by moving aircraft (and some scenery) folders to an external HD if and when I feel I don't fly them, thereby leaving the favorite aircraft in the sim.
So there is an additional 150.0 Gb for FS9 and 8.6 Gb for FSX of inactive aircraft, manuals, paint kits, etc. on an external drive.
This does not include the full copies of each sim on other portable drives used as backups in case of a reinstall, etc.