Auto-scaling versus manual scaling in cloud infrastructure.

Hey everyone, I've been thinking a lot about how we manage our cloud resources, especially since traffic can change so much. We mostly use auto-scaling right now, and it's pretty good at handling sudden busy periods. But, I'm curious if manual scaling, even though it's more work, might be better for saving money or being more predictable sometimes. What do you all think? When has manual scaling worked out better for you, or when did auto-scaling cause surprise costs or headaches?