They sound expensive that way for a paciThe Bandit Leader is not undead and takes quite a few Expert crits to take him down. If you can't take him on yourself with non-Pacifists, post the fact you require a Dungeon Key in the 'Wanted' board.
Addendum: Or find someone willing to sell one in-game.
I don't think I'll be able to afford the key for quite some time.