Distilling it down into "any particular advertising campaign" is pretty myopic in this world. It's about strategy as a whole over decades. Not every ad campaign is to drive immediate sales or signups (direct response). Branding and awareness campaigns can take years to run, and these are ALL diligently measured at every stage. Losses do occur do to negligence, malice, and poor execution all the time, but the brands should take some blame as well as they often feel compelled to spend. They have huge budgets that they NEED to spend regardless of they perform - sometimes due to accounting shenanigans, sometimes because they don't know any better, etc.
No matter what time scale you pick, there's still a point where ad spending costs more than you benefit. As time passes, the boost from any campaign decays. For any particular person you only need to show them so many ads to maintain awareness.
> these are ALL diligently measured at every stage
Mmm. Sometimes. Sure, you can obsessively measure audience and sales numbers, but if you don't have any controls then it becomes nearly impossible to figure out how much of that came from ads and how much came from everything else in the entire world.
it is true that that profit/loss point exists, but it may be impossible to measure. But it's very clear that 75+ years of Coca Cola marketing strategy has produced the situation where any human on earth immediately associates "Coca Cola" with soft drink.
If Coca Cola cut advertising 90% this afternoon, they likely wouldn't see the consequences until a new generation or two grew up.
