Why is round trip so much cheaper?

Question

A one way to Cairo, Egypt costs $800 while a round trip returning two weeks later is only $1200. I'd like to fly into Cairo and then fly out of Amman, Jordan. Anyone know why the airlines charge more for one-way?

Answer 1

Round-trip is cheaper because they know you'll be flying them again on the way back - guaranteed money means a discount.  Otherwise, what's to prevent someone from booking the cheapest one-way to their destination, and then another cheap one-way home on a different airline?