The notion that prison is only for “housing criminals” is just wrong, and leads to the fucked up legal system you see in the US. Its primary purpose should be reforming someone to become a better person, drop their old ways and rejoin society. The percentage of people who can’t be reformed is vanishingly small if you do it right. And even in those cases, murdering someone just because they require resources to live is wrong. They are still human beings, however fucked up their actions, and deserve life and dignity simply because of that.

Capital punishment is state sanctioned, that is the only difference in my eyes.

No, the main difference is the active and actual threat the person poses. When they are isolated in prison already, they do not pose any further threat.

Hooray, we are back to killing people for economic reasons!

I’d rather have him redistribute his fortunes to the relatives of victims. Making prisoners pay for their stay feels reaaaaally icky to me.