The packages are $9.99 now on their website and do include some stuff you get with the ball, so to me the price isn't that out of line for a fitness toy.
Still, most gyms have barrels of these balls. I think (my opinion, not sure of the facts, but have been told this by a previous gym) the Silver Sneakers programs for older exercisers have a special line of these they provide gyms that have their program with.
The balls at the gym tend to have a better quality for exercise, they're made the same way the good big balls are and aren't going to pop on you. They're also more comfortable to use than the $1.99 drugstore balls, which are hard and cheap (in my opinion).
There really are a lot of exercise uses for these little balls and this isn't a bad price, in my opinion, for a package like this, but if you're in a gym, you might want to see if you could just grab one of those for some moves.