Let's play the devil's advocate and understand the motive behind it-

The average annual wage of a Chinese citizen is $7,500 USD, whereas the average annual wage of an American is $45,000.

Which means that $400,000 is worth 400,000 x 45,000 / 7,500 = $2,400,000 . And that's only over 23 years so far. You have to keep paying until the day the victim dies. That's the equivalent of $105,000 for Americans per year.

If you refuse to pay, the victim will take you to court and confiscate all your belongings. If you still refuse to get a job to pay, the court will throw your ass in jail and (here is the important part) force your family to pay, indefinitely, until the victim dies.

So are you going to have your family pays $105,000 per year while you sit in jail, or are you going to make sure the victim is dead?

Trust me when I say no one wants to kill another human, but when the law is lay against you in such way, well don't be surprise that humans can override their natural instinct.

(I am from Hong Kong that, while most people there do not share the same sentiment, but can understand the math behind this horrific logic.

I don't know if that's the general nature of people though - I think when people have enough, but not too much, they're generally good. But if you're below or above that middle bound, things start to go bad. If you're below, natural hunger and base instincts for survival drive your behavior. But if you're above that "safe" level, it seems like a lot of people go a little wonky - lots of people who get to a significantly higher level, it's almost like it sets off a switch in their brain and it turns into a game, where they can't resist seeing how much they can get, damn the consequences.