@grislybutter Good point - "millionaires" may not be a good measure of the disposable wealth in our society.
I was trying to make a point about the market for ultra high end luxury goods being very deep and I would make the same point by saying that there seems to be a race in the high end audio industry to introduce extremely expensive products. All of the evidence I see indicates that there is no limit to what people will pay for ultra expensive stereo gear.
Is seems that every month a company introduces a new six-figure audio component. There must be a selection of at least 50 speaker models that cost over $100k and dozens of other components that cost over $50k. The anecdotal evidence is that wealthy audiophiles wait in line to buy this stuff. In an interview with Dan D'Agostino he said that he is selling his Relentless $250,000 amplifiers as fast as he can make them. There are other similar anecdotes from manufacturers including Wilson regarding their top end speakers. They sell out their entire production run shortly after the model is announced.
The other piece of evidence is the number of new high end audio stores that have opened in the last decade. They seem to be thriving. To go along with this, the two surviving audio publications seem to be very healthy with each issue getting thicker with more advertising.
So I guess my answer to the original question is to say that boutique audio companies haven't found the upper limit to how much money some people will pay for audio gear. I don't know how many people have $1 million+ in disposable income but there sure seems to be a lot of them.