How do you know what the best tubing for your frame is?
Even if you did, the price difference between top end steel tubing and average steel tubing is only 100-150 bucks, so the major costs in making a frame are the labour and loving attention to detail in sticking the thing together.
If you want to have a play with costings, just open up a spreadsheet and go for your life.
Let me know if you actually enjoy this and I'll let you do mine for me.