Six months after launch, OpenAI's ChatGPT advertising platform has published no normalised performance benchmarks across industries or campaign types. Search Engine Journal's analysis of real advertiser data from the period shows extreme variance: Hostinger spent nearly $70,000 at CPMs above $65 and reported traffic quality concerns; Common Thread Collective achieved a $4.41 average CPC and estimated 3.3x–6.8x ROAS on a $9,620 e-commerce test; a B2B campaign running at $9.29 CPC produced five accounts matching the advertiser's ideal customer profile out of 146 trackable organisations. Geographic CPC spread for identical campaign configurations ranged from $5.10 in the UK to $22.89 in New Zealand. OpenAI advises advertisers to start Max CPC bids at $3–$5 while simultaneously acknowledging that no industry benchmarks exist against which to evaluate those numbers. The operational consequence for Q4 planning is specific: brands cannot defend ChatGPT Ads spend to finance teams using the benchmark vocabulary — average CPC by category, industry CPM norms, expected ROAS ranges — that exists for Google and Meta because OpenAI has not published it. Treat ChatGPT Ads as an exploratory budget line for Q4 2026, sized accordingly, with explicit measurement agreements about what constitutes success before spend begins.