They do in a way. They absolutely use supply and demand to price their seats. They charge a price that they feel serves their goal of covering cost plus profit and assuring a full aircraft for efficiency. It is not the same cost for everyone. If you order 3 months out your seat is typically cheaper. If you try to get a flight 24 hrs before it leaves and its full, you pay a lot more for your seat. The same process should apply to solving their problem of selling more seats than they know they have. If they offer $100 on a half empty flight and get takers, fine. If not, offer more until supply and demand solves the problem they created. Its all a math game. If the math does not work, simply don’t sell more seats that you have. Simple solution. Just don’t penalize paying customers for your mistake or hopefully, the market will penalize you severely.