It would be a very different kind of evaluation, but the importance would matter differently if it were the /last/ 500 humans we were talking about - and there was a 90% chance that all would live and a 10% chance that all would die on one pathway versus a guaranteed 100 dying on the other pathway. But since they are just /some group/ of 500 humans with presumedly other groups other places, it is worth the investment - gambling in this way pays out in less lives lost, on average.