We all know that water will kill wicked witches, right? So
then washing anything with water would be positively hazardous to their health,
right? But they'll need to get their laundry done somehow. So that's why dry
cleaners for wicked witches would be such a growth market right now. You just
have to be good enough at black magic to offer enough of a threat so they'd pay
their dry cleaning bill. Unless, hmm: maybe if you claimed you used really
toxic chemicals that polluted the environment, they'd pay you anyway plus give
you a tip, seeing as how they're wicked. Plus, since money is the root of all
evil, they probably like spreading it around anyway, huh? And they can probably
just whip some up using magic too, so it's not like it costs them anything.