There is at least one additional aspect of the cost argument against the death penalty I should mention. It's related to the first three, but merits separate notation.
The argument is a phony from the getgo.
Those making it are attempting only to appeal to gullible conservatives. Left to their own devices in any other context in government spending, they could care less. Where, except with respect to the death penalty and punishment costs, have they shown even quasi-serious concern with frugality? Health care? Social Security? Income maintenance? Environmental subsidies? And on the criminal side: Rehab? Re-entry? Psychological counseling? Life skills? Which one of those programs (the first three of which exponentially outstrip the costs of the death penalty) have they proposed to cut back to any degree whatever?
Correct. None. To the contrary, liberals overwhelmingly support more spending for each, see, e.g., this so-called "report" proposing more than $200 billion in new criminal justice spending.
Abolitionists have gone the "frugality" route in a display of hypocrisy that would make Anthony Wiener blush. They don't give a hoot about savings; they just want to pretend to (until November 9).