Amp design logic

The price of anything is always what someone is willing to pay for it. A $50K amp that has never been sold is not worth $50K, it is really quite simple.
OTOH some of the "best" parts prices (called components by manufacturers BTW) are higher than you might imagine . Look up Deuland capacitors for instance and think of multiples of that cost.
Labor/benefits costs also seems to matter greatly. I needn't tell you that some populus countries that are making most of the consumer electronics now, have very low costs. In fact all overhead costs energy, space etc. vary widely by place of manufacture.
Many things we covet are kept intentionally scarce and never marked down these have a quote a pride of ownership cost assiciated (Think Patek Phillipe, Cartier, ST DuPont) etc.) Certainly this phenomena is part of this hobby.
Don't forget patented proprietary circuit designs. A lot of manufacturers do not release diagrams (schematics) and code parts with their own numbers, making duplcation and reverse engineering very difficult.
Well that is a start but when you finish your perfectly built DIY $50K, for only ?$1K?? let us all know if it sounds as good as the original.
But in the end only the demand will ultimately decide the price.

You're right that the total components don't nearly add up to $50k. What you're basically paying for, apart from good design and execution, is for the most part the sheer mystique that such a product has - especially the mystique that becomes attached to it as soon as it's given a $50k price tag. You and I are clearly not the intended buyers for a product as this. We've spent at least some time getting to know audio gear to some degree in some technical way or another...that is, we've bothered to in effect actually glimpse the little man behind the curtain of this industry. And why did we go there in the first place? Because we understood that buying outright the kind and quality of gear that we knew would likely be necessary for us from the outset was going to be more expensive than we could afford...so instead of giving up on our dreams, we decided to figure out a way to do things as cheaply as possible ourselves and 'learn from the ground up' to enlighten ourselves as to what it would take to do more for less. We may have that kind of time, but there are others who are perhaps married to their careers or whatever who simply don't want to have to spend so much time, effort and energy just trying to figure out where to start. What they want is for someone that they feel has already taken the guesswork of it all out for them. These people may feel it a privilege of their level of income that they indeed don't have to bother with any of that. Their approach to audio

(oops, hit the post button too soon). These people approach buying audio the way they may buy a new car for themselves - they may ask their friends what they like, take a peek on the internet to see what folks are saying about it and they may also pay attention to the advertising. Will I be buying a Mercedes or a Jag or a Rolls?? To a real degree it may come down to status perhaps more than anything else, but, for them, attempting to get inside the heads of manufacturers long enough to second guess them at every turn is perhaps an unassailable task, so they willingly trust makers to do as they will. But, since these people live in a world of advertising and word of mouth (and word of mouth based on advertising) and little else on the subject, I think it instructive to see that their willingness to rely on what makers say fits like a hand in a glove to how such items are priced. So what's the difference between a $50k amp and a $10k one? For the well-heeled non-audiophiles like them, one of them must be more special than the other. For us, usually about $40k... :o) It's interesting to me that many of us audiophiles also fall victim the further up they move on the industry food chain. Once you've spent that $50k on a component it's that much more difficult to proclaim it to be significantly no different than that $10k one. Of course some audiophiles in these pages have been there and done that and have said to have later come their senses, but makers know that there's always that next audiophile that may take the bait. But, these days are hard times for everybody and $50k amps are reportedly indeed a tough sell, even at the very few number of units it takes for it to be worthwhile.

I am surprising myself by asking the same sort of question lately about vintage after dragging an HK Citation 16 out of the closet manufactured in around 1975. A google search tells me that some audiophiles buying vintage and upgrading or having upgrades are very happy with the result. I don't know that I'm completely sold but I'm sure I've been undervalueing vintage. We might not need all the new amps, let alone a $50,000 one.

Take your own advice, just build your own. After you learn to solder, of course. I'm sure it will sound stellar. Hell, start your own business and grab a piece of the highend pie.