It's an interesting idea but you bring up a good point about the cost. Personally, I would rather not have to pay for a murder to be in jail much less be cryonically preserved.

But it sounds very logical. And probably the costs would balance out because we wouldn't be paying the prison costs, education, lawyer fees, etc. just the cost to keep the person cryonically preserved.

Ethically thought it doesn't seem right because it could just be prolonging the person's penalty. Still, an interesting thought.