Besides the block reward, how are miners paid — and what happens once coin issuance ends?

If a transaction's outputs are worth less than its inputs, the difference is a fee added to the block reward; once all coins are issued, miners can live on fees alone — making the system completely inflation-free.

Transaction fee = input value − output value. Any leftover is claimed by the miner of the block that includes the transaction, on top of the coinbase reward.

Bitcoin has a predetermined total supply. As that ceiling is reached, the block subsidy can fall to zero and incentives transition entirely to fees — so no new coins ever need to be minted, and the currency is inflation-free.

Go deeper:

• Controlled supply — Bitcoin Wiki — the halving schedule, the ~21-million cap, and the planned handover from block subsidy to fees.