The body of evidence overwhelmingly shows capital punishment cases cost substantially more than life imprisonment cases at every stage. While the moral and ethical efficacy of the death penalty may still be debated, from a practical cost perspective, the evidence clearly suggests it is much more expensive for taxpayers than sentencing convicts to life in prison without parole.
It’s more expensive to execute someone than to have them serve life in prison.
https://www.restonyc.com/is-it-cheaper-to-imprison-or-execute/
https://sites.psu.edu/bleonard/2020/11/30/the-death-penalty-v-life-in-prison/
https://www.researchgate.net/publication/324804378_The_Death_Penalty_vs_Life_Incarceration_A_Financial_Analysis