Well, in many cases comparing apples to oranges. $40k may only be medium price in high wattage solid state high end amps. Watts cost money and the better those watts the greater the cost.
Now I'm at other end of scale, prefer low wattage SET amps, very low parts count, circuits design long ago amortized, all the money goes into output and power transformers. Kondo Audio Note only SET I'm aware of that approaches $40k.
So, it depends on the context when one speaks of $40k amp, this only mid to upper grade compared to other high wattage SS amp, In world where $100K plus amps exist $40k is relatively low cost. Compared to SET where virtually no $40k amp exists this out of this world price. $40K as an objective price to compare with all other amps is meaningless for me.