If Apple doesn't want crap parts being used by repair shops they should sell the parts in the open market, regardless of the shop being in a "repair program", like every car manufacturer does
Car manufacturers make very few "parts" themselves. Gearboxes, as an example, are often designed and manufactured by companies like ZF[0] or Valeo[1]. They also sell these to the public at (usually significantly) elevated costs. I'm sure this could be done for specific Apple parts, but like the car manufacturers, Apple will want some control over the parts they design.
Exactly. So why can I go into an auto parts shop and buy the original Ford Spark Plug set for my model (which of course is made by an OEM) but not an Apple repair part?
It’s actually not. You can be sure that there will be manufacturers out there who will skimp on quality to make some money at a lower price, and repair shops will buy that stuff to grow their margins.
There are plenty of things (e.g. phone cases) that are sold on the open market, but they still get knocked off, and those knockoffs sell because they are cheap.
> there will be manufacturers out there who will skimp on quality to make some money at a lower price, and repair shops will buy that stuff to grow their margins.
This exists already. Apple is denying the consumer to purchase a legitimate Apple part to fix the issue unless they take it to an "Apple authorized repair shop"
It's that simple.