OK... Here are some rough % by section..
A. Amplifier stage 10-15% Will vary depending philosophy of brand, amount of overdesign. Major costs are amount of heat sinking, output devices.
B. Power supply 15-20%
As posted previously the power transformer is the most expensive single internal component, again will vary depending upon philosophy of brand, amount of overdesign
C. Royalties 8-15%
Depends upon # of channels, SW room EQ, type of SW DSP processing SD, HD, video
D. Processor power/resources 10-15%
Depends upon total software burden load for connectivity, audio, video, system control
E. Metal works, chassis 3-7%
Depends upon product size
Just my $0.02...