metalsupermarket prices.... ug, use them if you're completely desperate. I don't know where you live, but most steel and aluminum suppliers sell to non-business customers on a cash basis.
E.g. 1 5/8 DOM tubing for a 22' length is normally about $120 - not nearly $10.00 a foot as they are advertising. Add the cost of shipping and that would be 3 to 4 times as more than you'd pay a local supplier.
if there isn't a local supplier, calling sheet metal (like HVAC) shops and asking to be able to order metal when they get their shipments can be pretty cost effective too. The key is they get delivered at least $1,000 of material in a shipment - then you can really save bucks (and you don't have to buy what they're buying, just have to buy what their supplier sells),