If you’ve run any Google ad campaigns in the last couple of years, you’ve probably heard about Performance Max (PMax). Maybe you’ve even tried it but were left wondering: Where exactly is my budget going? And, what is my ROI from PMax campaigns? If so, you’re not alone.
Since its launch in November 2021, PMax has made some big promises to advertisers, like the AI-enhanced ability to reach the right audience wherever they’re browsing, including Search, YouTube, Gmail, Discover, Maps, and Display.
The catch? Advertisers have been stuck in the dark — unable to see how their spend was split across those channels.
But Google’s latest update to PMax is changing all of that. A new “Share of Cost” feature is finally revealing how your budget is being allocated. And it’s a game changer. Here’s a look at how this new level of transparency can unlock more PMax success stories.
Why “Share of Cost” Is So Important for PMax Success Stories
“Since the beginning of PMax, one of the biggest mysteries and frustrations has been its so-called ‘black box’ of spend allocation,” explained Benjamin Rorie, Vice President of Paid Media and SEO at The Threadgill Agency. “That lack of visibility made it difficult to evaluate performance, justify investments, or explain outcomes to clients.”
Now, it’s a whole new day for PMax and its users.
“With the Share of Cost toggle update, we’ve unlocked a new level of transparency,” Rorie added. “We can finally identify which ad placements are truly carrying the load and which ones are simply along for the ride — and share that with our clients.”
Measurable Impact: PMax Campaign Case Studies
At The Threadgill Agency, we’ve been reviewing advertisers’ latest campaigns to see what insights we can glean from this new layer of visibility. One of those PMax case studies is a PMax campaign that ran for 60 days, ending in July 2025. That campaign drove 674 conversions at a CPA (cost per acquisition) of $153.
The spend breakdown — now readily available in PMax — revealed several surprising insights:
- 90% of spend went to Search, with a CPA of $150.25.
- YouTube captured just over 8% of spend, delivering conversions at a CPA of $171.70 (that does not include any view-through conversions, so actual impact may be more substantial).
- Discover and Gmail barely registered, representing less than 1% of spend combined.
- Display was negligible, with spend under 0.25%.
“For months, we had seen occasional weeks where PMax campaigns appeared to dump impressions in bulk,” said Rorie. “Until now, the assumption was that these were low-quality Display impressions. This new reporting makes clear that the surges were actually skewing heavily toward YouTube, not Display.”
It’s a distinction that’s critical.
With YouTube, if a user doesn’t interact with the ad by either watching a significant portion of the video or clicking through on it, the advertiser is not charged. So, in effect, those impressions are creating incremental branding value at no cost.
“More importantly, the fact that Google’s bidding algorithm is allocating a meaningful budget to video suggests it sees YouTube as a pivotal step in the conversion journey for this client,” added Rorie.
And data supports that conclusion.
PMax Best Practices and Opportunities
These PMax case study results provide valuable insights for future steps. Here are some PMax best practices and opportunities that Threadgill identified for this client based on the data:
- Give YouTube more attention. With YouTube performance measuring stronger than anticipated, the branding lift from unpaid impressions makes this placement even more valuable. Stronger creative assets could unlock even greater efficiency, too.
- Search remains the workhorse. With nearly all spend going to Search, opportunities remain in testing final URL expansion and diversifying asset groups to capture more varied user intent.
- Acquisition settings are worth testing. PMax now provides the visibility to pair budget allocation with the new customer acquisition toggle. Continued testing and analysis will help ensure that spend is directed toward net-new growth.
How to Succeed with PMax
“For digital marketers, this Share of Cost visibility is more than a reporting tweak,” said Rorie. “It is a shift toward accountability in one of Google’s most powerful campaign types — and, most importantly, it provides clarity on Google’s own algorithmic decision-making.”
While PMax is still far from fully transparent, the Share of Cost toggle gives the visibility needed to make smarter creative investments, test audiences more strategically, and align spend more closely with goals. All of that equates to more Performance Max success stories.
At The Threadgill Agency, we know that the constant evolution of digital marketing and the constantly shifting algorithms are a challenge. But we also see these changes as valuable opportunities. They’re happening for everyone — including your competitors. If you’re looking for an agile partner to help you maximize these changes and leverage data to achieve a competitive advantage, let’s chat.