I am a huge fans of these movies. Amazon has them on sale for $7.49 each (they also have Math Circus for $7.49, although I have never seen it).
I seriously cannot say enough good about them--Leap Frog should hire me! My two year old knows all of his letters and sounds thanks to Letter Factory, and just today we started watching Word Factory.
I paid full price for both of the movies and still feel like it was a good deal.