My $18 CPM hack that actually holds up after 3 months of testing

Three months back I started capping my daily spend at $50 per ad set instead of letting the algorithm run wild, and my cost per thousand impressions dropped from $24 to $18 almost overnight. I know everyone says budget caps kill reach, but my CPA actually went down too, which made no sense to me until a buddy explained it forces the system to find cheaper placements. Has anyone else tried tight daily caps and seen the same thing, or did I just get lucky with a weird niche?

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hall.nina1mo ago

The part about it forcing the system to find cheaper placements is the key thing here, and it goes even further than that. When you cap the daily spend, you're basically telling the algo it can't just dump your money into the same expensive spots it defaults to, so it starts digging into the leftover inventory nobody bids on. I saw this with a retargeting set where the cap pushed me into some weird off-brand placements I'd never have picked myself, and the CTR actually held steady. The catch is you have to babysit it for the first week or two, because sometimes it finds junk that converts once and then dies. Once it settles though, the floor on your CPM stays low because the system knows it can't just spend its way out of a bad placement. Three months is a solid run, so you probably found a real pattern and not just a fluke.

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