But hey, it's thin and light and aluminum, so all is forgiven, right? Don't get me wrong, the MBP is a pretty gorgeous device, but it's pretty hilarious to say that all is good and well just because it's thin and light and aluminum.
The problem is that not everyone has the budget to buy a fully-speced machine at the time of initial purchase. Also, many laptop vendors charge a significant premium to buy such configurations.
Apple partly solves this by simply not even selling the low-speced "base model" that other vendors would advertise. But still, buying low/mid-range now and upgrading later can be significantly more tolerable on the wallet than going-for-broke every major upgrade cycle.
Yes. In some markets Apple offers financing options right on their website. In case of businesses, they can deal directly with their banks.
If you don't need macOS or an ultra-elegant thin computer with an incredible screen, you'll probably be happier with a PC from Dell or Lenovo with similar specs and an updated machine every 2 years. But they are neither elegant, nor thin. At least they run Linux very well.
My current personal laptop is 4.5 years old and I am now considering replacing it with a machine with specs similar to the PC I described - non-thin, non-elegant, decent-but-not-incredible screen, a non-bleeding-edge CPU, as much memory as possible, some flash storage and a hard disk and I don't expect to upgrade it in less than 5 years.