Would it be worth it for China to prop them up? I get that they're communism buddies or whatever, but what does China get out of it? What does China really need from North Korea?
From the Chinese and Russian (Soviet) perspective, letting a few Koreans get oppressed is worth it considering the alternative, a land border with the US
China can has influence over North Korea rather than it will be US (don't forget that there are two Koreas because USA and USSR both wanted to rule Korea but couldn't win against each other).