I disagree with the idea that it was solely because of the timing of the booking. I travel for business and have to book travel generally one week out. I know the prices that are charged for these trips. For example, I know that I could never fly Philadelphia to Boston with only 1 weeks notice because the flight (less than an hour) had a price of about $1,000 for a RT ticket to fly out early morning and come back at the end of the work day. The only carriers handling that route were US Air/United. Needless to say I took Amtrak the night before and stayed an extra day. Much cheaper.

Fast forward to the last time I had to make that trip (about 3 weeks ago), Southwest has begun to fly that route. My price, when purchasing a ticket 1 week out, was $275 (on United). Only one reason for me that the price dropped $700. Competition.