The students in my framebuilding classes pay on average about $400 for frame materials if they use all investment cast parts and standard True Temper or some other brand of tubing. That includes braze on bits and bridging. It is possible to reduce this cost if you look for specials suppliers have. It takes about an ounce of silver (now at $35) and a pound of flux around $12 to make one frame. You will need twice that for practice. A Henry James lug set runs about $100. It is possible to use old stamped lugs, bottom bracket shell and forged dropouts for much cheaper but they increase the risk of failure for someone inexperienced in brazing. On top of that you will want to buy at least 6 ft of straight gauge 4130 .035 wall tubing in various diameters for practice. It costs between $3 and $4 a foot. If you don’t have a good teacher you’ll need a lot more. You will put a lot of time and effort into making a frame if you want it to turn out decent so it doesn’t make any sense to reduce the outcome with cheap materials.