Comment by GuB-42

First thing is that Facebook makes money by showing ads, not by selling the product shown on the ad.

Second thing is that besides a small minority of people who refuse to buy advertised products out of spite, some would be blockers still do if the ad get shown. Maybe less than those without ad blockers, but still more than zero.

Third thing is that the point of advertising is not just direct sales. Some companies put up ads just to "take space", to establish themselves as leaders in their sector and not let others in. That's why you see som much advertisement for Coca-Cola. They don't expect you to buy a can of Coke just after you have seen the ad, you probably already have some in your fridge anyways. But by doing that, they make sure that when you want a drink, you think about Coca-Cola and not something else.