In the bitcoin world, they earn a mining reward of 12.5 BTC.

The mining reward will eventually drop to 0 BTC though.

the idea is that by that time there will be so many transactions that the fees will fill that. also, if users are also miners they have an incentive to continue the BTC network for their own self benefit even if the fees were less.

> the idea is that by that time there will be so many transactions that the fees will fill that

This comes with its own scalability issues which are currently unsolved (and might well be unsolvable)

> also, if users are also miners they have an incentive to continue the BTC network for their own self benefit even if the fees were less.

This is equivalent to the users themselves paying fees, but much less secure, stable, and decentralized.