You are being payed by SteemIt or by the software behind steemit with votes.
Important to note here is that you are not being payed real money, you will get a Cryptocurrency that the software behind steemit can generate infinatly.
The money comes from selling this Cryptocurrency on the market like you would bitcoin, if someone pays you for the Cryptocurrency you get the money.
So Cryptocurrency is made out of nothing?
Jup you could create your own and give you 1.000.000 worth your currencie, but it is only worth as much as people are willing to pay