The current block reward is ~300.000USD
Each block contains ~2800 transactions on average.
So far so good. That means that currently each confirmed transaction
is worth over $100. Later when there will be no block
Reward its expected that miners are paid by transaction fee.
But there is no way people are gonna pay 100$ Worth of btc per transaction.
Let’s be realistic and say people will pay 2$ per transaction. This is only 2% of the
reward of the current mining system.
Yes, for now transaction fees are not enough, and moreover I don’t think there is any payment method where you will have to be something more than for a little transactions, unless for huge amount of transaction. For now the way that miners can be making their profit is through the reward they receive from mining and the transactions fees they are getting can be a bonus.
By the time all the bitcoins are mined, which is going to be a very long time, there will be a solution to how miners are going to profit from the market. And by the way, by then there will be lots of transactions on the blockchain, and maybe the mining wouldn’t be as difficult and energy-wasting as it is now.