First off, I would never buy a new selfbow sold for $40. That's the going rate for a decent hickory stave. I would think it would have to be crappy. I've even seen many with price tags on them of $200-300 that weren't good enough... for me. Any of the selfbows that I would even consider owning had price tags on them of several hundreds of dollars... which is too rich for my blood... which is one reason I make my own
I believe he's made hundreds. There's a guy near me that's made hundreds in a short amount of time and they're very rough. In bomaking, quantity doesn't inherently bring quality.
However, a new bowyer with a few basic, previous woodworking skills, extreme attention to detail, a strong desire to make each one better than the last, with a goal to reach a level of refinement with his bows that few possess... can turn out VERY nice selfbows in very short order.
For some folks however, those sort of things just aren't important, and as long as their bows 'survive' for a couple dozen shots, they're ok with it.
There's really no excuse for uneven string grooves, excessive set, an uncomfortable handle, poor finish, etc. after hundreds of bows made... ESPECIALLY when selling them... for ANY price.
As Dean Torges wrote in his book 'Hunting The Osage Bow'... "Just because it's primitive, doesn't mean it has to be crude."