Here is a site with a set of tubing bender plans that you can download for free. http://www.chopperhandbook.com/bender.htm
How true you can go to a regular steel supply yard and get what you need and they cut it for free for about a thired of what the box stores sell it for.........Curtit seems cheap till you start pricing the cost of the dies and add up the cost being you need separate dies for each size of tubing both round and square. That being said by buying offcuts/drops from the metal yard. Or finding a scrapyard that has the sizes you need you can buy the steel much cheaper then online or from the box stores that have a HUGE markup on steel and sell in such small chunks. Now for the smaller lighter tubing it is possible to make dies by laminating hardwood togather for limited use/hobby