Interesting observation Jeff. I never saw it that way but it becomes quite obvious when pointed out someone else.
I sent a note to Winegard to see if someone could correct the issue. We will see if they clear up the confusion.
Just to be clear, the replacement (amplified) head and new boom is $49.99 (I have seen it on-line for a bit less) and the $129.99 is the entire mount, arm and antenna.
You don't have to use the new boom. It is shorter than the existing pole for the Sensar so you don't get quite the height but it might it on a windy day.