The Seat Cost Curve: Why Frontier AI Assistants Reprice Agency Delivery Before They Reprice Headcount

Frontier assistants are not a headcount decision, they are a delivery-cost decision. The gap between agencies that route work through a standardised assistant stack and those that do not shows up as margin per retainer, not as a hiring freeze. Model choice now moves both invoice cost and output quality on the same client job, so the routing decision is a pricing decision.