It's a reward for solving the block, and comes from nowhere except the work required to solve the block.
So again at the end you create blocks wich are added to the system.
For creating these you get a BTC bounty wich is much more worth in USD/EUR then you put in at the beginning in the form of electricity.
And this bounty is paid by a tiny x % of the total amount of BTC avaialable in the system?
So all people who own bitcoins and invested USD/EUR in them pay you indirectly for mining and basicly lose money?
Sorry for maybe asking the same question in a different way.
But my guts just never trusted systems that say you get free money (BTC -> EURO/USD) for doing almost nothing (mining).
At the end it comes around as the following:
2 euro - > Electricty -> Mining -> 1 BTC -> 15 euro
Profit = 13 euro for just running your mining rig all day.
But who pay for these 13 euros that just got created when mining?
For what it's worth. You cannot mine on electricity alone. You also have to have a motherboard, cpu, graphics card (or 2, 3, 4, 5, 6 of them), power supply, network AND the electricity to run it all. Oh yea, and the time and knowledge to get it all running.
Saying mining's only cost is electricity is like saying you can dig for gold with only gasoline as a cost.