With work done, not with headcount. The base never moves; the token line grows as Heidi does more, answers, jobs, agents, which means the bill grows in proportion to delivered value and falls every time model prices drop.
This is the inverse of seat pricing, where doubling the team doubles the bill before anyone gains a thing. With Heidi, doubling the team barely moves the bill; delegating twice as much work moves it, and that growth is the good kind.
Caps keep the growth intentional: raise the ceiling when you decide to delegate more, not when a renewal negotiation decides for you.