A subversion of the Even Evil Has Standards
trope, when a villain refuses to to something abhorrent not because it too horrible, but rather because it is too inefficient, ineffective, or he could have done something better with them. Often with the implication that he found this out through first-hand experience.
- In the Order Of The Stick prequel series Start Of Darkness, Xykon refused to do any villainous scheme involving deflowering virgins. Because it's like giving a guy who doesn't know carpentry a hammer and expecting him to build you a house.
- In (admittedly what I read on the TV Tropes only) the Draka series, the Draka are horrified at the Holocaust. Because the death camps were a massive waste of resources.