Most people hire contractors because they can't do it themself. Or if they can, they can't get a professional result. Since I don't have that problem I do my own stuff. I have written about my background before. So it is not like I am average when it comes to fabricating just about anything.
Every single home I have ever owned I have done at least a couple projects on. The only thing I hire out is roofing due to the physical demands and whenever I need countertops I will have the fabricating shop install. Also carpet, I can't stand messing around with carpet.