I think the price increase for the Denon 8500 and marantz 8805 to the new versions is absurd! No difference except hdmi 2.1
So there's not been an increase in the cost of materials and or labour in the time that has elapsed between when those models you mention were launched and when the models that replace them were launched?
The average cost of a house was under £2K in the 1950s. Even if you just take inflation into consideration then this would equate to about £65K now.
Like it or lump it, prices do and will increase over time. If they don't then you should be asking yourself why that is the case and what are the manufacturers skimping on in order to keep their prices so low?