At Predjamski Grad, Slovenia, we were charged for using toilet.
1 Euro and I could use clean and well maintained toilet, I don't mind paying a little for confort.
What interesting was I received a 1 Euro coupon at the gift shop.
So technically the toilet fee is free if you buy some gift.
Of course there is no gift you can buy at 1 Euro, almost automatically they can make some than 1 Euro.
Coupon is a strong marketing tool. Some people get obsessed to use it.
Interesting marketing connection with necessary facility and unnecessary purchasing behavior.
(I did not use the coupon by the way, even though I am a big coupon user)