Some math:
At today's prices of roughly $230 USD per bitcoin, 3600 bitcoins per day are valued at about $828,000 USD. That means it is roughly that much mining/electricity cost per day to mine bitcoins and to secure the network.
Wrong assumption
At current difficulty, for big miners it costs ~40 USD to mine one bitcoin. 230 USD is not the cost. It is the revenue they are making now for each bitcoin out of 40 USD investment. Net profit is around (230-40) = 190 USD, which is used partly to cover their initial investment.