The show is free, you just need to stake out your viewing spot early. The "special seating area" stuff, however, does come with a price (I don't know how much it is since the Disney link is down). You do not need to do that, however, to view the show.
Here's a "Tip" from the Disneyland webpage:
"Fantasmic Tip
Arrive early to obtain seating for Fantasmic! and parades. Major viewing areas are usually filled closer to show time. If there is a second Fantasmic! show, enjoy the second show. There are generally less Guests at that show."