The cost of replacing a sash window will depend on many factors including: style, size, material and glazing. A wooden sash window will cost significantly more than a uPVC sash window. A wooden sash window can cost up to £1000. Wooden windows are more expensive to manufacture so expect to pay that bit more. uPVC sash windows can be designed to mimic wood and are much cheaper in price. The starting price for a standard uPVC sash window is on average £525.