In game were fighting difficult monsters and bosses having a traditional repair system like in a action rpg makes no sense. You should not penalize players for trying a boss over and over again.
I think you need to reevaluate the need for repairs and maybe add the cost to enchantments etc if you want to lower players gold. Repairs is such an old school system that most action rpgs try to avoid these days, but with souls combat system, it works against the core of the game by punish players that need to learn a fight.