According to the Blockchain.info: Cost per Transaction, the latest "Cost per Transaction" value is 16 USD. Apparently, it's not the transaction fee, what does it mean then?
On the chart overview page you find the description "Cost per Transaction: A chart showing miners revenue divided by the number of transactions.".
Meaning, it's the total value of the block reward of a block divided by the number of transactions confirmed on the network in that block.
Here is an example with made up numbers:
- Block reward is
25 BTC + 0.1 BTCin transaction fees.
- There are
502transactions in the block.
- Current exchange rate is
25.1 BTC / 502 transactions = 0.05 BTC per transaction
367.30 USD/BTC * 0.05 BTC per transaction = $18.37 per transaction
Concerning what will happen after the regular block reward is reduced/discontinued, check out: