Last time I went to buy square tubing they quoted me over $100 a stick. I'm going to head down there this next week and see what I can get for angle and channel, as you'd be the luckiest man alive to find whole 20' lengths at a scrapyard of anything that isn't massive 2' or larger structural steel.
I scrap cars and junk for trade (when they have anything worth trading for) and scrap trailers and rv's for the straight channel, box, or I beam, axles for tubing, spindles for anything that needs to rotate.. (firewood processor here I come) The downside to this is what is left over from rv's, plenty of wood, plastic, and fiberglass that gets hauled to the dump. I usually break even with quite a bit of metal toward projects if it's sheeted in aluminum. I pass on anything fiberglass.
Life would be rather simple if we could all afford to buy new things, however, where is the challenge in that? I'd get bored pretty fast.