I can't criticize too much, because I do absolutely nothing with metal-fab, or vehicle work or mechanics. However, even I can tell the Tuettels are far from the pinnacle of custom chopper work.
It seems to me they start with a stock-pre-fabbed frame, and then weld up a funny gas-tank, and tack on a bunch of water-jet cutout do-dads... over and over and over. Punctuated with some P.R. theme bike reveal, a few family fights, and some demo-derby in the parking lot.
Meanwhile, I recall watching Jesse James, who kicked off the whole "Custom Chopper Cable Show" phenomena with a few small documentaries, fabbing up a frame from pipe-stock by hand with a blowtorch, a vise, and bending it with his belly while wearing a leather apron and a few asbestos pads using a wooden jig that catches fire to match the curve he wanted.
And even further than that, in brief glimpses you see those chopper and motorcycle conventions, there's guys working out of complete hole in the wall shops that are making completely gonzo bikes up from scratch, with very advanced stuff like Buell-style fuel-in-frame, and design work that looks as finished as anything Harley-Davidson or any of the Japanese makers puts out.