I've ordered tubing and collectors to do a set of 6-1 headers in mild steel. Looks like I'll have about $3000 total invested once done, but that includes a fair amount of tooling as well. A second set would likely cost me about $1500. This is for 24 to 30 inches of equal length primary tubing (tubing length will ultimately be decided by fitment) in 1.75" diameter. If I can sell the first set for what I have invested, the tooling will ultimately be free, and I may even start building them out of stainless.