Facebook reached $27B revenue last year (2016) as there are millions of pages advertising their products and services on this platform. Facebook has not standart ads prices, beacuse it depends on supply and demand. But we can get some statistics from Facebook Ads Manager page and can create approximate statistics.
You can see ad prices for 10 countries (Azerbaijan, it’s neighbour countries and popular countries). Prices calculated at 10:00 AM (GMT) on 18th february, 2018: