The PMP floor versus open-exchange arbitrage nobody audits

The PMP floor versus open-exchange arbitrage nobody audits

Buyers often pay a Private Marketplace floor for inventory that is simultaneously available cheaper on the open exchange. The arbitrage exists because the two markets are priced by different mechanisms, and almost no one reconciles them.

The structure:
— A PMP floor is negotiated and fixed: you agree to a minimum CPM for guaranteed-quality, often guaranteed-access inventory.
— The open exchange prices the same publisher's impressions dynamically by auction, which on low-demand impressions can clear well below your PMP floor.
— So you can be paying a fixed 8 dollar PMP floor for an impression whose open-exchange clearing price that moment is 4 dollars.

The reconciliation:
— Fingerprint impressions (publisher, placement, user, timestamp) across your PMP and open-exchange logs to find the same inventory in both.
— Compare your PMP price paid against the contemporaneous open-exchange clearing price for matched impressions.
— The PMP premium is justified only by what it uniquely buys: priority in the SSP waterfall, viewability or brand-safety guarantees, or access you can't get on the open exchange.

When the matched open-exchange price is consistently below your floor and the PMP offers no access or quality guarantee you actually need, the deal is a structured overpay.

Why it matters: a PMP is worth its floor only when the floor buys something the open auction can't deliver. Reconciling matched impressions across both markets is the only way to see whether you're paying for priority or just paying more.