$20k too much for 6 double glazed thermally broken windows and 2 slider doors?

The quote includes 5 large windows, each one approx 2.4m x 1.5m, 1 smaller bathroom window approx 1.2m x 0.6m and 2 slider doors 2.4m wide, 2.1m high. Windows are custom sizes to fit existing frames in an old house. All are double glazed aluminium, thermally broken. Quote is excluding GST. Location is Melbourne.

Can anyone give a sense check on this please?