Instiller Volume-to-Margin Curve

Instiller prices on email volume, not client count: £325 per month covers 100,000 sends with unlimited client accounts, and each additional email above that band costs £0.0033. That structure rewards agencies that consolidate many small clients onto one account rather than opening a plan per client. A ten-client roster each sending 8,000 emails a month totals 80,000 sends, still inside the base fee, so the agency's cost per client sits near £32.50 before any markup. Push the same roster past 100,000 combined sends and the overage stays linear at £0.0033 per email, which is easy to absorb inside a retainer. The framework: model total roster volume first, price retainers against the blended cost, and treat the 100,000 band as the line where per-client margin either holds or starts to thin.