Notre Dame
Everything is expensive for tourists. Within 3 blocks of this place in any direction, I'm sure you can grab a can of coke for $4, not to mention the souveniers. Interestingly though, entering the church is free. Hopefully they get a cut of the souveniers.
When you think about how wealthy France is versus how much it produces and how much it taxes, something doesn't add up. That is until you realize that France has more tourists than any other country. More foreigners go to France in a year than to the entire US. I was suprised about this, but it's true.