Hi all, I've had a C64 sitting unused for years because I can't figure out how to hook it up to any displays that I have. When I was a kid I used it to learn BASIC by writing programs I got in magazines and play games (Impossible Mission and F-15 Strike Eagle being my favorites), but it's sat unused ...

Have you looked those items up on Ebay? Its how I valuate items before I sell them. I've learned that something is only worth what people will pay for it, regardless of what pricing guides say they're worth, especially "collector's"items.