Earlier quoted context omitted.
Even if we had 100% certainty what crimes are 100% worth death? Not even that is simple. If you want to consider cost, it costs literal millions to execute someone.
Plus what of the potential profit? The guilty person could be a teenager making a silly mistake who could grow up to become the next Einstein. Insert Bill Gates' mugshot here, who is responsible for hundreds of thousands of jobs and bringing billions into the US / worldwide economy. But he was guilty and it would probably have been better to execute him because what if he did something else wrong?
I'm so tired of the "next Einstein" pithy replies. These are adults who have done heinous crimes against innocent people. Justice requires severe consequences.