Well said! However I think you are over-estimating a lot of cyclists out there now that you are on this side of the educated fence. When I got back to cycling, I had no ideas of this custom build business and how good it can get. But it really is through a lot of reading and time do I now have a better feel of this subject. And when you are a busy person with a comfortable budget, picking up a boutique wheel from a known brand is that much easier. It's one decision + $$$ vs 7 decisions (type of rim, type of spoke, type of hub, type of lace pattern, type of nipple, colours, who to build) + lack of demonstrator + uncertainty of result. The other issue of geography. Where I am, wheel builders with a reputation aren't that easy to find.
Then there are many people out there who's just flushed with money (see dot com boom), who doesn't care about price. It's a lost cause there.