[idunno246]

My understanding is It's built in what happens when it's too expensive to mine by adding transaction fees. Or once there are no more coins to mine. The network still needs to verify, so the person in the transfer offers up coins to get it verified which go to the miners.

[humbledrone]

It is correct that after 21 million Bitcoins have been mined, other incentives will be required for mining to continue. Transaction fees are the likely choice.

If Bitcoin became a major currency, I think there might be other incentives, too. To speculate: a large government might want to run mining operations to make it more difficult for other governments to collude against them in a 51% attack. Of course if they did this, they'd probably want to pick up transaction fees as well.