I bought a few more tickets at the airport today, and I had estimated it would be around $130. It ended up being $140. Being curious, when I got home I went in and dissected each ticket, and found that one of the flights had a $14.99 "Passenger usage" fee instead of the $19.99 that I normally see. 2 tickets with that smaller discount made up the $10 difference. What is really strange, is I booked the exact same flight a month later, and it had the $19.99 fee. I guess it probably will pay to double check the fee before going all the way to the airport in the future.