They take pains to make games for months - months or even years - years to create a good game.
Her question, where the developers of a game to get income or input from the results of his work? The answer is very simple, namely the cash purchase (with money) in order to be played can be more powerful.
I take the example of Game Clash Of Clans. In the game Clash Of Clans no such thing as gems. Gems here use very much at all. From to accelerate building / buildings to be able to buy gold / elixir / dark elixir.
So early plays Clash Of Clans it is advisable not to use gems to speed up the building or buying gold / elixir. Gems in the game COC is very important, use gems just to buy a builder alone.
But to get it can be said easily. Only by completing some quests / achievement that the COC. Gems can be obtained free of charge from the complete achievement.
Here is the achievement that can be solved to get the gems without having to buy:
1250 trophy get 450 gems
2000 trophy get 250 gems
2600 trophy get 1000 gems
3200 trophy get 2000 gems
