AAdvantage Miles

I can't say that I understand the way airlines work.  I was looking for a one way flight from Barcelona to Rochester for April 2017.  If I wanted to buy a ticket from American the price of the fare that was available was twice as much as a round trip.

I wanted to use points and when I first got on to look when the date was available that we wanted, it was 30K points for an EconomyMilesSAAver flight with a great flight direct from Barcelona to Philadelphia and then Philadelphia to Rochester.  I didn't book it right away since it seemed so early and we wanted to be sure that we were going to stay in Barcelona for a few days after a cruise, before we went home.

Two days later I went back on and that same flight was now