Today, before military strikes began on Syria, White House Press Secretary Josh Earnest was asked how much the administration was expecting military operations against ISIS were going to cost. They have no idea. Not even an estimate. From The Hill:

"I don't have an estimate on that," Earnest said. "I know that we're interested in having an open dialogue with Congress to ensure that our military has the resources necessary to carry out the mission that the president has laid out." So far, the administration has relied on the Overseas Contingency Operations budget to pay for operations against the terrorist group. The White House had previously requested a cut in that pool — from $85 billion to $58.6 billion — for the next fiscal year, but lawmakers decided instead to keep funding at current levels in the temporary budget measure passed last week. The White House also indicated it would seek funding for the effort against ISIS from international partners. So far, more than 40 countries have said they would support a coalition effort against the terror network.

As we've all experienced, "having an open dialogue with Congress" means the administration will complain bitterly about even the slightest effort to restrain whatever it wants to do.

As a possible benchmark, a Pentagon spokesperson says current military operations in Iraq—air strikes, security, and surveillance flights—cost about $7.5 million per day, according to The Hill.

Update: A reminder from the ISIS debate last week. Congress authorized $500 million to train 5,000 Syrian rebels over the next year.