Like the day before you’re ready to travel the price for the seat is half of what it was for the previous month. At Future.Travel we see this scenario quite often. It has to do with the airline releasing more inventory. Perhaps it is inventory from other markets that finally gets pulled into the last 24 hours of sales.
As to why this should not be cheaper the closer to the travel date has a lot to do with profitability. In most cases the flight has already reached the break even point of being cost-effective. Each added Passenger/ passenger baggage is a cost of extra fuel that has to be factored into the equation. Hard cargo, freight, is easier to To sell and calculate than The variable of a passenger walking on, maybe. Second to that is because They have already made the profit, by hitting break even, they want to maximise any profit they make so the price will be higher.