Agreed that cost should NOT be a variable in a decision of this type.
"It is more expensive to care for a lifer in prison than an execution."
Simple googling will show this to be inaccurate. Studies vary, but the anecdotal "think of the medical costs, etc." doesn't defeat actual numbers. That executions cost more is widely know by all sides.
Just one of MANY articles reporting on the actual studies (not anecdotes) that have looked at the issue.