I admire the skills of custom bike builders and own a custom bike myself, but is a custom bike better than a well sized quality, mass produced bike? I can see custom being useful if you are very tall, short or have some other non-standard physical requirements, but for most riders custom bikes are really about vanity.
That is so many shades of wrong.
Starting at the bottom, even if it is a mater of vanity, which is pretty much something you can say about any purchase that touches our dreams etc... Our nature. People quite clearly are all jazzed about who their LHT makes them out to be also. Even if so, so what? people still need to know where to buy them. Reverse snobbism is just as much snobbism as snobbism. The only requirement for bike touring is a bike that works better than walking at any level you wish to chose (slow but I get to sit down, is fine). Everything else is not necessary. And what is more, there is someone out there having a far better time than you, and doing more with about that level of gear.
I admire the skills of custom bike builders and own a custom bike myself, but is a custom bike better than a well sized quality, mass produced bike?
Obviously yes, better, in hundreds of ways. I think the term "custom" really doesn't describe what it is all about, or one end of it can be about, and one can pull a Clinton on the "meaning of better". But really in what realm of human endeavour is the cheap crap, the short cut, the ugly, the inexperienced, etc.. just right up there with the best. When you buy a production frame you are buying Walmart quality, you are just getting 10 dollar a set tubing, rather than the anodized aluminum, suspension set with the miles of perfect dimes on it of the Walmart bike. It just happens there is a far larger demand for bikes that don't make a kid drop his chocolate bar in the parking lot pot hole, than there are for bikes for serious touring. We pay what we pay not because the frames are more elite, but because there market is small.
Custom bikes are not about vanity entirely. Some people like nice stuff. The good, or better, experience the computer salesmen are always talking about. This is why we prefer to do stuff like tour in nice places. A nice touring location is satisfying, a nice bike is satisfying. Together it is a better experience. Money is tight for me, but there are millions of wealthy people out there, some of them buy bikes.
When one sets out to make a perfect custom frame on looks at the bike and the racks and bags as a whole, and designs every single part to be perfect for it's use and to suit the rider perfectly, there are hundreds of possible improvements and upgrades, no compromises, or kludges.
The underlying sensible question is what difference all this makes. As you say, there is the whole fit thing. That is huge. I think it makes sense that better designed and executed equipment contributes more than just satisfaction, there should be an efficiency piece, and a reliability piece. But the overlooked part is that a lot of touring is actually a low mileage use compared to stuff like racing, and commuting. It can be awkward the places where gear breaks down, comparatively. Overall, the good gear is certainly better, but you do not need it to play.
I think when we compare comsumer attitudes, what I see are a lot of people who own a large number of expensive, but third rate bikes. Like some of those listed under your name (depends a lot on execution of those builds). You see the same thing in fashion. One can get a pretty good tailored suit for the price of a half dozen pairs of jeans and some expensive T-shirts. There are many people who end up with hundreds of those cheap garments in their wardrobe, and who could have easily assembled a decent set of basic clothes, tailor made. Of course in either case there are good reasons for having more crap. But there is also the fact that custom stuff is not marketed as heavily, and we are taught to believe the nonsense that at some level the cheap junk in altogether better. We buy high margin brand crap over lower margin, better quality expensive gear, that requires more commitment to own. All fine, just so long as we know we are being played.
As far as the relatively routine skills involved in making the frames, not something to be all that fussed about. There are millions of people with skill of that kind in the world. It takes a special extra something to run a small boutique business, and in addition, some of the makers are stars of a sort. Combine all these things, and there are some skilful people involved, but we shouldn't exaggerate the importance of the skill. The product is still the key part of the deal, and it needs to justify itself moreso than because the person making it has some routine set of skills.