My first thought was the exceptions. And so yes, you can't say "Human life is worthless." But if you look around, there's plenty of evidence that, in fact, it sometimes is. For people who value something else more. Such as victory, profit, or whatever. There's also the issue that in-group lives tend to matter far more, by orders of magnitude, than out-group lives. I've seen quotes from famous people using 10^3 or more.