Average or minimum price is 40 euros.
The stadium won't be full... they are complaining a lot about the prices in Italy. Also, you can't buy CL tickets in season packages like they do in Serie A. So, with tickets for each match set apart, they get more expensive.
Also, a great part of the fans who go to the stadium are not from Turin. Since it's a weekday, it's tougher to go back at night and work in the following day. And it's night and Turin is a freezing city.
So... I think the stadium will be full only against Chelsea in the 1st stage.