So far a couple of your opinions are 100% proven wrong:
1. fact: in first world countries it is more expensive to kill someone via death penalty than have them serve in life in prison. Its seems counter-intuitive but there are tremendous legal fees to consider when killing someone via death penalty.
2.fact: the death penalty does not deter violent crime. Canada's rate of violent crime actually went down once the death penalty was abolished.
You seem pretty opinionated, thats cool and all, but for your sake you might want to educate yourself on the matter. Fact > opinion.
It is more expensive to kill someone via the death penalty because of the endless delays in the execution date through the appeal process in the US. This has happened only in the last few decades. In the 1800's and maybe up to the 1960's, the time between conviction and execution was relatively short in the US. Richard Hauptmann, the kidnapper of Charles Lindburgh, was convicted on Feb. 13, 1935 and executed April 3, 1936. A little over a year. Now some convicted and sentenced murderers are on death row for decades.