Flight prices fluctuate according to how many seats are available on the particular flight, how much interest that date is generating on the website and of course, the time of year. It's not by accident that prices are sky high once school is out. That's what most people want anyway....a holiday in high season when the days are longest and the sun is at its highest height.
If there wasn't so much interest from the public then prices would be a lot lower because the fine an airline has to pay if it misses its slot at one airport and is late on arrival at its destination, is astronomical!! Also, don't forget that a pilot is limited as to his flying hours. Those Charter jets must be kept in the air!! So, if we all stay at home for a couple of years, prices will drop but we'll all be flying scheduled and that'll be way more expensive and involve more than one flight in most cases, e.g. a flight to Dalaman would definitely incur a change in Istanbul. This is never going to happen of course.....but in view of the cost of Pilot, First Officer, cabin crew, fuel, taxes, maintainance of the aircraft, slots, air traffic control.....I could go on, and on, flights are not, in fact, very expensive.