it all depends who you ask? to a wealthy person, $40k will not mean much to someone. to a middle class indvidual, he may be able to afford it, but wil rationalize and think what the $40k can do for himself and his family.
now for the questions of listeing/diference between $10k vs. $40k amp.
I was lucky enough to hear a Gryphon Antileon Evo, excellent sounding like many other amps I've listen to. Would I purchae the $40k Gryphon? I would not, the small differenes between them isn't as noticeable as one would think. But I can't be the judge of it as what I hear, may not be what someone else likes.
the life of a need and a want. wealthy people could not be satisfied with $10k amp just knowing it doesn't cost as much.
also like others have said, is the amp $40k build? how much of a percentage is taken out for marketing? distriubtion? sales?
enjoy music friends.