I was about to mention that the cost in the US of imposing the death penalty is considered to be higher than imprisonment, but I think that is because of the endless appeals that are allowed.  I haven't read your link yet so maybe it says that.

I would only be for the death penalty in the cases I mentioned above (terrorists and mass murderers), and only if there is no conceivable doubt about their crimes. If there is no doubt, why not get on with it instead of leaving people on death row for decades? Who benefits, other than lawyers?