Targeting may increase what advertisers will spend per eyeball, but it also reduces the number of eyeballs they have to pay for.
Selecting a target audience may increase the cost that advertisers pay, but they don't have to pay for as many people 
mnli hypothesis: Selecting a target audience may increase the cost that advertisers pay, but they don't have to pay for as many people  premise: Targeting may increase what advertisers will spend per eyeball, but it also reduces the number of eyeballs they have to pay for.