Originally Posted by
Bojay1997
I don't know, both the C64 and PC versions are ports of the Apple II original. The last two nice complete copies I saw sold on Ebay for the Apple II version went for $55 and $80 respectively. I did see a sealed mint copy for the C64 go for around $125 a few months back. It's somewhat valuable, but I don't think you'll break $100 with a used complete copy even with crazy collectors.
Flight Simulator is a sub-$20 game most of the time and the scenery packs pop up constantly. The C64 version is really not considered terribly collectible.