I have an economics background, so I often work solving problems with limited resources. I also work extensively with the law, and have given expert witness testimony, though primarily in civil cases, not criminal ones. But that does give me perspective on what it costs to bring a case to court.

This Nevada report shows that death penalty murder cases are almost four times as expensive as non-capital murder cases. Put this together with Nevada being a much more conservative state compared with other states, and therefore much less 'criminal friendly' than average, and I think I'm justified in guessing that the cost difference would be way, way more in other states (like California, my home state). In some locations, many rounds of mandatory appeals (often over a decade or more of time) increase the cost up to 10-15 times a non-death penalty murder case.

"So if your wife was raped or daughter beaten to a pulp..."

Would it be nice if everybody got that attention, a full prosecution budget? Yes. But that's not the world we live in. If I was in this situation, and demanded a death penalty trial in Nevada, my potentially selfish request would be taking up enough taxpayer resources to fund 2-3 other murder cases: without proper funding, the criminals would go free, or the State of Nevada would most likely bargain with the criminals for reduced sentences, so that the prosecutors would have the time to perform the extra steps required to prosecute a death penalty case. And the choice to not support the death penalty is not protecting a criminal's life, as you suggest. In the view from my desk, it's about maximizing the punishment for all criminals, rather than forcing resources to be focused on relatively few.

"So let's say there's 100% proof."

That's a nice assumption, but that doesn't change the cost structure. A prosecuting attorney isn't going to go ahead with a case that isn't really, really solid. The costs I'm talking about assume 100% proof, and they still don't always work out - remember that the facts of the case and evidence usable at trial are two entirely different things, and juries are complete and total crapshoots capable of making bad verdicts.

I understand your point, that you want these criminals to die, and that's not the problem. But I'm commenting here to make sure that you know the consequences of what you are asking. Am I in favor of reducing mandatory appeals, and other things that raise the cost of capital punishment? Yes. Am I favor of making these crimes eligible for capital punishment? Sure.