How Does Increasing Transaction Fees Affect a Miner’s Revenue When Difficulty Is High?

Transaction fees act as a secondary revenue stream for miners, supplementing the block reward. When difficulty is high, the block reward's value in terms of effort is diminished.

Therefore, higher transaction fees become crucial, as they can offset the reduced profitability from the block reward. In times of network congestion, high fees can sometimes even surpass the value of the block reward itself.