Lucky you that there is more than two colluding "competitor" steel stations.
In the white darn city here, the prices are within 1 cent of each other and everyone somehow raises them whenever there is any excuse.
Differences between cities are up to 20 percent. Sometimes (not considering externalities) it would be worth driving much farther to buy petrol. Few people do it.
Local monopoly or collusion is as good as global one. For Google Pay, the local is whole main Android store.
Where they do compete with cheaper alternatives (e.g. in South Korea), the premium is lower. But only there.
Facebook essentially guesses a price on their advertisement monopoly on their platform. The price is not set by competition nor by demand, but by belief in value added (which is only partially responsive to supply and demand), just like in most stocks.
I recommend reading on the concept of elasticity and substitute good, as well as idiosyncracies of human economical decisions.