[roland00]

Note this is a first order effect, what I explained above.

The 2nd order effect is that by making more money for the same ad, while your competitors would make less money from the same ad...you can either sit on that profit.

Or you can use your market share and guaranteed profit to make ads less profitable to competitors and this creates a positive feedback cycle where Facebook Ads get more and more market share but other competitors and platforms of Ads gets less and less, which in turn actually allows Facebook to charge more per Ad in the long run (but in the short run Facebook may want to decrease the price per Ad.)