Many cities now have HFH "Restore" stores. These are centers that are repositories for all kinds of things house, including, but not limited to overstock for HFH projects. Many builders will donate their extras to the Restore stores. It's amazing how much stuff you can find for a fraction of the cost. Duel- and triple-pane windows, lumber, all kinds of brackets and nuts and bolts, paving stones, flooring, carpeting, duct work, you name it. If it's used in construction or remodeling, you'll find it there. Some of the stuff is new and some is used, but it's all in very good condition. I saw a HUGE, brand new Duel-pane Bay Window there for $300.00! It was picture window size. Here's the website for our local one but you should be able to find one in your area.
http://www.restorefresno.org/