PDR1
All the arguments in your post 26 apply equally to medical equipment, which itself is often a rip off but peanuts in comparison with aviation parts. The reality is that manufacturers charge what they can get away with. They know the aircraft cant be returned to service without their part or overhaul and they have a monopoly.
They would jack up medical equipment to the same level if they could, but as it normally gets charged to an individual patient it would be affordable. Sadly they see aircraft owners as having bottomless pockets, or at least owning items with massive capital cost that are worthless bits of scrap metal unless you pay up.
Dont think you will get much support for your views on this forum