Mattel's 6" TV Show '66 Batmobile was $50 bucks and seated 2 figures. They also made a huge electronic Tumbler for 5" figure that had lights, noise and pop up features for $30.
$100 is high, even with electronics. As long as the vehicle is quality though, I don't mind that price tag. Once I see Batman and Robin sitting in there, I'll probably forget all about the price. And like Sallah mentioned, it's just an MSRP. A lot of vendors will probably offer it for less. I know I got a '66 Batmobile for 20 bucks when they had it on sale on Amazon.