I think the line can be drawn by your enjoyment of DIYing. I love the challenge, problem solving and pride in one of a kind gear. But with that pride comes a little stress when I miss the mark. As far as saving money, It's two fold. 1st, if you enjoy the process then your time doesn't count as a cost (No fair getting paid to have fun). Secondly: obsessive research, good instructive resources, preoccupation, over-thinking, and over-measuring are a must. Otherwise you'll eat up your savings in material. Nice thing about this type of DIY is you can usually "un-sew" and try again. From what I gather stairs are much less forgiving.