Mining costs millions of dollars per day in electricity costs. I guess we can just expect a few people to burn a hole in their pocket for the good of the network?
Mining only costs a lot because coin value is high and the block reward is high. This means miners are willing to spend more to win the reward.
As the block reward lowers then mining becomes funded entirely by equilibrium-priced fees.
My own estimation is between $400k per day (hard lower bound) and $800k per day depending on assumptions about hardware efficiency, although around $100k / day was added in the last week in a trend that is continuing, so $1MM/day will very quickly be accurate.