Lots of reasons, including the following:
- 19 channels
- video capability, 8k hdmi don't come cheap.
- Multiple DSP functions, playability of multiple sound formats.
- Multiple Inputs, outputs, network capablity.
- 15 channels of power amps.d
- Large power supply for the power amps.
All those things cost, so something have to give, such as not using ICs including opamps, volume controls, dsp that have better specs. They do tend to use reasobably SOTA class DAC ICs on the flagship models, imo because that might make a lot of potential buyers think if the DAC ICs used are SOTA types, then the overall performance might just be SOTA too, unfortunately that's usually not the case.
Regardless, $2000 dac and amps, even without most of the above features, are not going to perform better. If you know of such a combination, I am sure I won't be the only one who want to look into it.