We found a great deal in Booking, 2 nights in a suit for 300 euros for 3 people. It was worth every penny.
The room was awesome, one big bathroom with bathtub, shower and toilet, and one powder room. The bed was big and comfortable and the extra bed was a convertible couch but comfortable. It has minibar, cable TV, good air conditioning.
The hotel facilities were really good, the spa is free and there was nobody so we enjoyed everything totally alone.
The breakfast was continental style, not the best but it had a little bit of everything ( eggs, bacon, bakery, fruit, cereals, toasts...) And good quality.
They have free parking. The location is good, 20 minutes walk to the old town, in my opinion a very enjoyable stroll. Being obsessed with staying in the centre centre of Mostar is moronic because is a city you can see in five minutes, so it's not bad to walk a little bit more.
The staff is nice and they recommend very nice places to eat and for nightlife.
The only inconvenience was that people smoke in the firestairs and I don't like that, but in Bosnia is allowed to smoke in enclosed spaces.