Prices being what they are in so many different countries, that would be difficult to determine, Mestre. Even U.S /Canadian prices vary by quite a bit. European prices are higher, from what I'm told.
Try this: determine the age of the camera. For each year, subtract about 8-10% of it's original value to come to an approximate value in today's dollars. This method is NOT carved in stone! It is just to give you a starting point. Other factors affect the value, such as number of actuations, esthetics, accessories included, etc.