nzkarit

Also January had their yearly new year sale, so why price would have been low then.

(Ignoring sales (and that they will often block dates where load already good))
The prices are always in flux. The computer's goal is the sell out the plane for the highest overall price. If sales are slower than expected price will go down a bit. Flight selling fast price goes up to gain most benefit. Price always high at the end as people traveling last minute need to travel so will pay & these are particularly business customers so not flying on their dime so less price sensitive.