Question about buying facebook accounts

Hi

I see that in my country some people buy facebook accounts(10-50€ piece) for 2-3day usage. They do something under advertising, after that your advertise account gets blocked.
Whats the point ? How they earn if someone let use they facebook? Can someone reveal the secret?

Hello, I see FB account is not easy to use deal to IP

FB account ask for some requiement, please notice with this