Upvote:2
You were scammed.
Taxi tariffs in Bosnia are usually somewhere in the range KM 1.00 to 1.50 per km and an initial fee of KM 2-3. Tariffs may be a bit higher during the night, but KM 11.60 sounds like a correct price for a 7km ride.
I have never been to a country where taxi meters do not show the local currency and there is no reason to believe that they don't in Bosnia. Even if the meter had shown β¬11.60, that should have been around KM 23 and not KM 30 as you were charged.