I visited Edinburgh over 20 years ago, and have a hazy recollection, of visiting the camera obscura, but the visibility wasn't very good, so I was charged a nominal amount to go to the top and admire what view was visible.
I'm assuming that the other attractions in the building have been added since.
On arrival we were sent straight to the top to see the camera obscura, which combines the view and knowledge of the guide.The views from the landing are stunning. We then browsed the other the other floors in descending order.
Some areas were quite busy, but it's all good fun, playing with optical illusions and the like.
Worth the money.