In the corridors where advertising capital flows, a quiet transformation is underway: the great holding companies have discovered a high-margin machine built on bundled AI tools and principal media, buying inventory wholesale and reselling it at undisclosed markups. The arrangement is lucrative precisely because it resists explanation — opacity is not a flaw in the model, it is the model. Marketers are left to choose between participation and disadvantage, while the industry's oldest promise — that an agent serves the client, not itself — strains under the weight of a new commercial logic.