Still not allowed to post a link, but found a site here vBulletin Hosting | Forum Hosting | vBulletin Support. (statelinesupply) .com/Handbook/Aluminum/Sheet-Plate.aspx that estimates 21 gauge at .456lbs per sq ft. If my 800 sq ft estimate were to be correct, that would be about $250 in scrap aluminum. Probably $50 in dump fees. So if I could pick it up for around $3-400, and put $200 back in my pocket from scrap and have a decent frame to work with, that may not be so bad.