Any additional costs are paid as normal
But if youre a Red deck thats really good at generating lots of mana maybe your Commander is Electro, Assaulting Battery or Neheb, the Eternal, Fire Nation Turret will be doing 50 damage pretty often
Its good, but without reprints, it wont be a commander you build around just because you found it in a booster and thought it was neat
Another thing in its favour is that it is more generic than Bloodbraid Elf and therefore fits cleanly into a wider range of strategies
Instead of flooding this list with all of them, Ill just throw them all together
You cant discard or sacrifice more to target more creatures, and you cant cast Ruthless Disposal at all if you dont have any other cards in hand or if you control no creatures