$800 Mac Mini (Apple's most affordable offering that runs macOS)
$90 Acer SB220Q Monitor
$200 Dell Inspiron 11 3000 (Most affordable Dell PC I could find being sold new)
$1200 One time payment for Visual Studio (but you don't get updates)
So if have to both buy a computer and need a full featured IDE then Visual Studio's license wipes out any savings you get from avoiding the "Apple tax". It gets even worse if you want perpetual updates to Visual Studio which cost $800/year but come free with XCode.
This is counter to what I had expected beforehand myself, I expected the "Apple tax" to make the bar of entry much higher than PC development.
If, on the other hand, you can get by with a less advanced IDE or are developing in a non-proprietary language like Java, Python, or Scala the cost goes way down:
$200 Windows/Linux laptop
$FREE Eclipse/JetBrains CE IDE/Visual Studio Code
This is certainly more affordable than the $800 macOS alternative. Although one could debate whether the above mentioned IDEs are on equal footing with XCode/Visual Studio.