Your CBO + open targeting campaign performs better at lower budgets because:
Budget spikes reset the learning phase – Meta needs time to re-optimize, which can hurt short-term performance.
Higher budgets broaden reach too fast – Meta starts targeting less qualified users.
CBO gets less efficient – It struggles to allocate higher spend smartly without fresh signals or creative variety.
What to Do:
- Scale slowly – Increase budget by max 20% every 2–3 days.
- Duplicate campaigns – Let each run with its own $50–$75 budget.
- Switch to ABO – Gain tighter control at ad set level.
- Rotate creatives – Prevent fatigue as ad frequency increases.