How to evaluate used bicycle price? Hey I am about to buy a used bicycle and recently I got offer for Peugeot bicycle. We both do not know the price to agree on...

The question is how to evaluate price of an used bicycle? (where to put the most focus)

The bike:


Age: around 10 years Gears (front and back): Shimano 105 (seems all
fine) 
Frame: used but still in very good shape 
Brand: Peugeot
Pic:



I guess no more info.
If you know the model and exact year Bicycle Blue Book is a good place to start. This is a link to all the models for Peugeot:

http://www.bicyclebluebook.com/BicycleDatabase.aspx?make=718