Agencies, in effect, earn a percentage of the spend. But this amount is determined up front. Clients go to market saying "We have $x for client y and we want to know which shops will give us the most bang for the buck."
Shops that over-promise then fail to maintain reasonable profit margins don't survive. At the same time, there's pressure on clients to work with established players, since a campaign gone bad is even harder to defend when it turns out the the marketing budget was blown on inexpedienced and / or desperate people who were willing to seriously undercut competitors just to land the account.
Shops that over-promise then fail to maintain reasonable profit margins don't survive. At the same time, there's pressure on clients to work with established players, since a campaign gone bad is even harder to defend when it turns out the the marketing budget was blown on inexpedienced and / or desperate people who were willing to seriously undercut competitors just to land the account.