We did the behind the scenes tour when we sailed the Carnival Miracle last December. Yes it is $95.00 per person but only 16 spots are available to take this tour.
When you get on the ship, you get a shore excursion guide. The tour was listed on the back page, I missed it but my wife saw it and we signed up as soon as was possible.
We greatly enjoyed the tour, and yes it is a little pricey, but it was really neat to see the inner workings of the ship and the bridge. Be aware that you do not see the engine room, but rather the engine control room. The engine room is off limits to passengers.