estimated replacement cost of either rear-end or differential on 2004 Volvo S60

purchasing the vehicle and was advised by the salesman that there is a noise in rear of the car. He thinks it may be either the rear-end or differential. we want to know if this is an expensive repair item. the vehicle has 94,000 miles.

Asked by for the 2004 Volvo S60
Is this an AWD S60?