Marketers buy the ads and then figure out their return on investment based on how many people click on them, "like" them (remember the value of a "like") or take some other action (sign up for a contest, download, etc.).

FORBES

Out of every 10 students who sign up at Smiles, only one can expect to make it as a model or succeed in a notable beauty contest.

CNN: ASIANOW - TIME Asia | Beauty and Bounty