Its "just" supply and demand, and whatever that causes by way of consequences. In this particular case, the cycle of diversity might be at play.
Although, anecdotal evidence would suggest that this is nothing particularly novel in the audio landscape.
Prices are all relative to general price levels and peoples incomes and wealth. A reasonably affordable yet kinda swish Sansui amp in about 1972 (when the Dow Jones was about 900) was perhaps a few hundred bucks.
How does that translate to today’s environment?