You can buy an aisle seat

I'm on a completely booked flight and as it started boarding they announced that if you had a middle seat you could buy an aisle seat for $29.  Since it's a completely booked flight that means that they are giving away the seats of late comers.  People that reserved aisle seats and who haven't shown up 30 minutes before departure will now be sitting in a middle seat when they show up.  And the airline will be $29 richer for each person that gets booted to a middle seat! 

They might also be selling my seat as I got a complimentary upgrade to business.

What will they think of next?