Agencies bill in three main ways, and offers across models can’t be compared on price - because the thing you’re buying is different in each.
The retainer
You pay a flat monthly fee for the agency’s work, regardless of results. It’s the most predictable model and a good fit when you want to build your own brand and keep full control. The risk is equally clear: all of the outcome risk sits with you. A retainer agency can be excellent - but its strongest incentive is that you renew.
What to look for: anything in the contract that ties the agency’s money to your result. We run managed campaigns on this model ourselves - but with a profitability guarantee written into the contract, because we think an agency should have skin in the game.
Pay-per-outcome
You pay per delivered unit: a qualified lead, a completed pitch, a held appointment - defined in writing before launch. The campaign risk (ads, creatives, testing) sits with the agency. It’s also the easiest model to model: you know the cost per outcome and your close rate, so the spreadsheet exists before the spend does.
What to look for: the exact written definition of what counts as billable, the replacement policy for outcomes that miss it, and real conversion numbers from your vertical. One honest limitation: an agency can only offer this in verticals where it has proven, repeatable campaigns. Anyone promising pay-per-outcome in any industry, on day one, is waving a red flag, not a selling point.
Revenue share
It sounds safest (“I only pay on closed deals”), but it’s the hardest to run honestly: it requires full reporting of your sales back to the agency, invites disputes over attribution, and effectively asks the agency to underwrite your sales team’s performance. That’s why very few offer it cleanly.
The one question that cuts through everything
“If the campaign fails, who loses money?” The answer tells you more than any pricing page. If the answer is “only you,” the fee should be low. If the agency shares the downside - per outcome or by guarantee - you’re paying for something real: transferring risk to the party with the data to carry it.