https://deathpenaltyinfo.org/policy-issues/costs

“ The death penalty is far more expensive than a system utilizing life-without-parole sentences as an alternative punishment. Some of the reasons for the high cost of the death penalty are the longer trials and appeals required when a person’s life is on the line, the need for more lawyers and experts on both sides of the case, and the relative rarity of executions. Most cases in which the death penalty is sought do not end up with the death penalty being imposed. And once a death sentence is imposed, the most likely outcome of the case is that the conviction or death sentence will be overturned in the courts. Most defendants who are sentenced to death essentially end up spending life in prison, but at a highly inflated cost because the death penalty was involved in the process.”