The chain
Your dollar goes to whoever runs your media, then to a demand-side platform, then through an exchange, then to a supply-side platform, then to the publisher whose site or app shows the ad. Data and verification vendors take slices along the way.
Each layer provides something real. Each also takes a percentage, and in many arrangements you cannot see any of the percentages.
Where the money goes
Industry studies of the programmatic supply chain have repeatedly found that a substantial share of gross spend — often a third or more — does not reach the publisher. The exact figure varies enormously by setup, and anyone quoting a precise universal number is guessing.
The important point is not the specific percentage. It is that the take is invisible by default.
The markup question
Some providers buy inventory and resell it to you at an undisclosed markup. You are quoted a CPM, you have no idea what they paid, and the difference is their margin.
That is not illegal and it is extremely common. It is also why two providers quoting the same CPM can be delivering very different amounts of actual media.
The alternative is a transparent arrangement: you see platform cost, you pay a stated fee, and the two are separate lines.
Questions that expose it
Is your fee separate from media cost, stated as a fee?
Do I see platform invoices or reporting at cost?
Do you take any rebate, discount, or incentive from the platforms you buy through?
Straight answers to those three tell you whether you are buying media or buying resold media.
What this means at local scale
At $2,000 a month, an invisible 30 percent take is $600 — more than most transparent execution fees. The markup is frequently the largest cost in the arrangement and the only one nobody discusses.
You do not need to audit the whole supply chain. You need your provider’s fee stated separately from the media, in writing.