If you are looking at it in price/year and think that old school amps last 30 years, keep in mind that recapping has costs. When somebody paid $2,200 in 1999 dollars for a Bryston 4B-ST, you better bet that they are going to get it serviced. When a McIntosh or Accuphase starts to hum, it goes to a workbench when a black box AVR would go to the graveyard.
Servicing these modern class D amps would make no sense beyond replacing a bad power supply. The whole amp costs less than the recap cost of one of the old monsters. These modern class D amps are not serviceable, but $100-300 devices were never going to be economic to do so.
I drive a Mercedes and was told the secret of Mercedes reliability. They have a good reputation for reliability but they truthfully aren't reliable as a Toyota. The reason for the reputation is i) it is more reliable than BMW and ii) Mercedes owners get they timely services and do repairs. When you have a 10-15 year old luxury car you still abide by the service interval and a $5,000 repair doesn't total the car. High end amps are the Mercedes of the audio world - you drive them to the dealership instead of driving them into the ground.
Also, a lot of these cheap Chinese amps these days are using better capacitors and better cooling that Hypex and Topping, respectively.