The main problem with this thinking—aside from any moral values, and the permanence of wrongful convictions—is who gets to decide on who “deserves” death. This was the reason WA’s supreme court struck down the death penalty in 2018 (read, this bill only reinforced a ban already in place via the justice system), as it ruled that the death penalty—as executed prior to 2018—was inherently a racist penalty. That is the rule in which it was applied, did so seemingly arbitrarily for equal crimes, while still following racial lines.

Your second argument holds no water. CA, which still has the death penalty, is spending way more money on death row prisoners than on prisoners sentenced to life without the possibility of parole.

EDIT: Since this is HN, the court decision in 2018 was directly based of a regression analysis by researchers in UW, the study is available here https://files.deathpenaltyinfo.org/legacy/documents/WashRace... (PDF)