A few things that stood out to me:
One alert is never enough. Treating alerting as a system, not a single email.
GCP pricing calculator in the deployment checklist, not an afterthought. You almost have to be obsessive about checking.
Hard caps: GCP doesn't have them. Budgets only send alerts, they don't stop charges. You can wire automation to disable billing but that's a hack, not a feature.
Cloud providers benefit financially from complexity and opaque defaults. I own my config mistakes, but the suggestions around capacity planning and realistic cost modeling were genuinely helpful.