This question comes up periodically. The answer in good part lies in the aesthetics. The faceplate is often the most expensive element. Then the rest such as the capacitors as mentioned, some use large banks of them, then volume ladders and other resistors, wire transformers and so on depending on the design.
Tube Amp Pricing
I’ve been curious about the costs
of tube gear. As far as my layman eyes can see, the components in tube amps
look similar. And yet, the pricing is all over the place - $30,000 to $1,000.
Is it the amount of engineering that explains the wide differences in cost, the
components, or a combination of the two? Just curious