Never, ever, ever assume there is any kind of logic that your average occupant of this particular reality could comprehend inside any given lifetime that explains how airlines work out what to splash across the screen (& how long for) as the price for any given seat on any given aircraft on any given route on any given day.
Just go on the assumption that whenever you do commit, it will be an inconveniently large random number that it you later compare price paid with the occupant of the seat either side of you will bear no relation whatsoever to what they have paid.