> So, even if a miner mines a block with only 0-fee transactions, they are still rewarded with a small amount of Bitcoin "from nowhere". Sure, but as long as t

> So, even if a miner mines a block with only 0-fee transactions, they are still rewarded with a small amount of Bitcoin "from nowhere". Sure, but as long as there are transactions with fees in the mempool, then mining 0-fee transactions has an opportunity cost. Currently that's about 5 BTC per block, compared to the 12.5 BTC reward (https://www.smartbit.com.au/charts/transaction-fees-per-block https://www.smartbit.com.au/charts/transaction-fees-per-bloc...). It's possible that forgoing the transaction fees will make mining for you unprofitable if margins are thin. Also, larger blocks are more likely to be orphaned, so including 0-transaction fees increases that risk (very slightly) with no additional reward (though currently the orphan rate appears to be basically zero, even with full blocks)