Why are Harbeth speakers expensive while its drivers are not.

I own a pair of Harbeth Super HL5's that I bought about ten years ago. I have always enjoyed them. So, maybe seven or eight years after I got my SHL 5's, Harbeth introduced the SHL 5 plus. I am not sure how many years Alan Shaw dedicated to refining the SHL 5 plus to make it better than the SHL 5. It was years, though, and he is a professional. He has all of the necessary resources and a particular aesthetic. He built upon a traditional speaker that dates back to the Spendor BC-1 and/or its BBC equivalent, the LS3/6. Suffice it to say, it's difficult, expensive and time-consuming to make a speaker like this better than its predecessors. If we want someone to do this, we need to pay for it and the cost of the SHL 5 plus reflects that work. It seems expensive to me, too, as do the other speakers produced by Harbeth including the 40.2, 30.1 and HLP3 ESR.

Harbeth is a successful company and is selling a very well-reviewed product in the SHL 5 plus. I don't know how many SHL 5's or SHL 5 plus speakers Harbeth has sold or will sell but I bet that it is not that many when one considers all of the work just to develop and refine the speaker. Maybe if SHL 5 plus speakers sold in quantities rivaling iPhones or big screen TV's, SHL 5 plus speakers would cost a whole lot less.

Like it or not, we participate in a hobby with not so many other people. It does not cost less to refine a product that sells relatively few sets than to refine a product that sells in greater quantities. And the fact that the SHL 5 plus costs $6,395 in the US means that not so many people can afford them. The U.S. Census Bureau reported in September 2014 that U.S. median household income was $51,939. It has almost certainly risen some since then but not enough to put a pair of SHL 5 plus speakers in every household. 

Were it as simple as building a pair of two cubic foot boxes, putting some stock drivers into them and soldering together a simple crossover to get a pair of speakers that better the Harbeths, wouldn't a lot of people just do that? In my mind, Harbeth owners hire Alan Shaw to work years and years to refine something that suits our taste and meets some reasonable technical standards. The cost of the materials is certainly relevant but, in my mind, does not represent the primary source of value.

"Selling at a lower price decreases revenue and creates a higher demand."

I can affirm from experience that is not always the case, particularly in a luxury or image-oriented market.  Without other info, people will first assume something is worth about what you charge for it, and will virtually never assume it is worth more than that!  Charge too little in hifi or software and sales will approach zero.

From what I can assess very expensive drive units aren't necessarily more than that: very expensive. I'm not saying they're incapable, but quality drivers can be made for much less (why then spend more?), and implementation is key. It seems to me the drivers in Harbeth speakers are capable of doing what they're meant to do, and a lot of research goes (and has gone) into their voicing and tonality by ear, to a degree that seems unequaled. The late Peter Snell chose rather standard looking drivers for the A/II model from Becker, Philips and Audax, but the speakers allegedly sounded wonderful (have only heard the later A/IIIi which was not of Mr. Snell's voicing, but a friend of mine has extensive experience with both models, and clearly favored the older A/II's). On the other hand, the Living Voice Vox Olympian's/Palladium's use drivers from UK-based Vitavox (among others) which cost downright fortunes (some £3,100/3,300 for the bass and midrange driver respectively, a piece), but these are clearly chosen following extensive tuning and implementation and for very specific purposes.
What's interesting is also Harbeth's attention towards enclosure "tuning," regarding them as an essential part of the overall sonic imprinting and contribution. Many if not most manufacturers seem almost (blindly) hellbent on killing vibrations first and foremost, rather than "playing along" with their contribution in having an ear for their signature, and this way they may end up with detrimental sonic by-products not intended. Going by the non-resonant enclosure approach, when rather successful, I find exposes the sound of the drive units all the more (and not necessarily for the good), and moreover has a tendency to deaden the sound in ways that comes off unnatural to my ears. Harbeth's approach seems a rather smart one, in that they combine a sensitive ear for live, natural sound, and knows how to apply or convert this into engineering and construction that will eventually present a fairly authentic sonic facsimile.    

Nice comment made by phusis...Not easy to make a speaker.  $100 for a tweeter isn't cheap by the way.  Focal inverted domes used to cost $45, morels for less than 50, dynaudio 6" could be had for $130, scan speaks woofer/midrange for less than $100... But putting it all together and making it sound its best is a long process of trials and errors.  The quality of the drivers is one thing, the expertise is really what makes a difference.

Well this is interesting. 

It seems to obvious to suggest that perhaps those far more expensive drivers would not...
A. Sound as good as the ones Harbreth uses.
B. Match the crossover.
C. Are as reliable.
D. Are as musical sounding.