I'm not a libertarian and I believe in intervention for humanitarian reasons on principle however the cost has to be considered not just the benefit. How many

I'm not a libertarian and I believe in intervention for humanitarian reasons on principle however the cost has to be considered not just the benefit. How many lives and injuries, (North Korean, South Korean and American/allied) would it be worth to free the survivors in North Korea? Even assuming China and Russia managed to stay out of it. There is a cost in life that would be worthwhile but there are also costs that would be too high. I would like it to be possible but I'm far from convinced it is. Practically any solution probably has to come through China or internal leadership succession.