Weird display of passenger fees

I have set my passenger fee to $15 but when a passenger enters/exits an aircraft the fee is displayed as $19, what is happening?

Fees get altered once you have a full board (to your benefit). One of the board members has the ability to increase income from passengers once they are hired, and additionally, they reduce salaries once they are hired. These are all percentage based. I believe if you open your Board of Directors screen, it tells you what each position unlocks/affords once someone is hired into that position.