Prior military, didn't fly planes, but worked with pilots and asked lots of questions. Cost would likely be a few thousand just to take off and land, and cost of fuel and pilot pay while they're in the air. Keep in mind though, pilots NEED flight hours to maintain their wings, else they get grounded and have to go through additional simulation training and a bunch of other stuff. We'd often have pilots make up reasons to fly back and forth between other bases, just to get their hours in.