Were you saying don't write automated tests that test your code, instead focus on monitoring the actual production invironment?
Or were you saying that specifically the "unit test" class of automated tests are not worth their time?
I can imagine a system that monitors the business metrics well enough to prevent defects from slipping into production (it's a stretch, metrics are soft and squishy moving targets), but I can't imagine using only those metrics to find every bug you ever slip into production. Metrics are so distant from the bug that caused their downturn; you'd waste so many cycles debugging. The gap between writing the code and finding the problem would be much larger than if unit tests found them; that has to slow things down as well.