I just want to point out that many times, first-class seats are not sold out as in the case for coach or economy class seats. In many cases, 'regular' people can play their cards right and get a free upgrade because there are unused seats.

If Ayumi didn't pay for them, there's a good chance that no one would've been sitting there anyway. I only thought about it since my friend is a flight attendant and she says that flight attendants have been known to sit in first class when they are not on duty because of empty seats.