maybe 1/2 inch or 1/4 inch and 5 feet length, 2 or 2 1/2 feet height, and 2 feet width. I can't really find any pricing on websites so I came here.
Call a glass shop--in the yellow pages under "glass" and ask them. You haven't given enough detail for anyone here to be able to tell you, even if we did know what prices are in your area.