Could you please tell me how much the border fee is when I rent a car from Sixt in Belgrade and drive to Bosnia and Herzegovina, Montenegro? Is it 40 euros for each country ?

I rented a car in Frankfurt and drove to the Netherlands and Denmark. The cross-border fees were all 10 euros, and the one to Poland was 40 euros.

Pay once and you're done.

It should be calculated by day.

There is a ceiling price.