Less than most advertisers assume, and this is not an argument for higher invoices but a useful fact at the negotiating table: you then know where there is give and where there is none.
The measured margin
From the annual accounts of Belgian agencies, financial year 2024, calculated in IKAg's Agency Barometer: the median agency kept about 22 percent of its gross margin as EBITDA, the bottom quartile about 7 percent. And 85.4 percent of agencies posted a positive EBITDA, meaning roughly one in seven ran a loss.
Note what that 22 percent is: a percentage of gross margin, so of the fee portion, not of your total budget. If half your budget goes to media and production, the profit on your account is half that percentage.
Why the margin is under pressure
Between 2021 and 2024, what an agency pays per person rose by 18.2 percent, of which 16.8 percentage points were automatic indexation. What an agency takes in per person rose by 9.8 percent over the same period. That gap of almost seven points is the vice the sector is in, and nobody in that sector chose it.
What to do with this
Not: assume there is plenty left to shave off. At an agency in the bottom quartile there is literally nothing to shave.
Instead: move the conversation from discount to scope. Do not ask "can this be ten percent cheaper", ask "which ten percent of this work can go". The first removes margin and therefore the people you most want; the second removes work you may not have needed.
And know that an agency running at seven percent margin does not invest. Not in people, not in work, not in what it will propose to you next year. That is not charity but your own interest, because next year you are buying from that same team.
See also: what a normal margin is, how to know whether an agency is healthy and is my agency too expensive.