That bike has a quill stem and downtube shifters. Cannondale road bikes haven't been made with a quill stem and downtube shifters in over 15 years. There is no way a 15+ year old road bike is worth $800 unless it's some sort of collector's item. This is probably either the original owner who thinks because he "paid $1,600 for it new" (back in the 90s) that it's worth $800 now. Or it's somebody who is just plain out of touch.

Offer $200 and stretch to $250 if it doesn't need a tune up or tires.

Functionally, this is the equivalent of buying a laptop that was made in 2004. It may work...but it's nothing special.