What Does a Media Buying Agency Do (and Cost)?

A media buying agency plans where and when your ads run, buys placements across platforms like Meta, Google and TikTok, and optimizes them toward targets such as ROAS, CAC or leads — while you keep ownership of your accounts and data.

Planning and buying are two different jobs

Media planning decides the strategy — which audiences, channels, budgets and timing will hit your goals. Media buying executes it — launching campaigns, bidding, optimizing and moving budget as results come in. A good agency does both, so the plan adapts to live performance instead of sitting in a slide deck.

When the same team plans and buys, nothing is lost in translation. The person who set the target is the person adjusting bids on a Tuesday afternoon.

What the work actually looks like

• Setting up and validating tracking so every platform optimizes on real revenue
• Structuring campaigns for learning, then scaling the winners
• Testing creative every week and retiring fatigued ads
• Reviewing search terms, placements and audiences to cut waste
• Reallocating budget across channels by marginal return
• Reporting on revenue, CAC and ROAS — not impressions

What it costs

Most agencies charge one of three ways: a percentage of ad spend, a flat monthly fee, or a hybrid with a performance bonus. Percentage models are common for smaller and mid-sized budgets and usually taper as spend grows; flat fees suit predictable budgets; hybrids align incentives when tracking is reliable.

Watch for hidden media markups. With a transparent agency you pay the platforms directly and see exactly what the fee is.

When you actually need one

If you are spending enough to generate real optimization data across more than one channel — and nobody in-house has the time or cross-channel expertise to run it properly — an agency usually pays for itself by cutting waste and improving signal. If you are very early or spending very little, focus on product and offer first.

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