Any source that equates justifiable homocide with murder should be laughed out of town. It would be more accurate to claim that the castle doctrine has saved taxpayers millions of dollars annually. Factoring in the reduced future robberies and injuries to victims as well as the cost of jailing the criminals and the number gets big fast.
here in MN, that’s around 40k per year.
It’d be cheaper to buy the murderer a house with inoperable doors and windows.