I've personally noticed and saved multiple $xx,xxx monthly cost billing spikes just by take a daily glance at our cost explorer. I'm in the AWS accounts every day doing investigative work anyway that an extra 30-60 seconds is trivial.
Seeing something "small" like an ECS task that is continuously failing to start properly because of a bug and repeatedly pulls a container image or a lambda function that's taking longer that it reasonably should (takes 5-10 seconds when it's normally a tens or a few hundred milliseconds) can dramatically drive up a bill in short order.
