What is with this younger generation?

Alex and I have an agreement that whenever she is entertaining her friends at our house and they make a mess and do not clean it up...all the girls owe me 5 bucks as a "maid" fee. Last night, Alex and her four friends decided to have a mac& cheese cookoff. (They frequently do this, where they break into teams and have a contest as to who can make the best tasting mac&cheese.) They didn't just stop at the mac&cheese, however, they decided to make smoothies to go along with the mac&cheese. All of this resulted in quite the disaster in the kitchen. I, of course, was not home because I was out running errands and such to keep the family going. So when I returned home and walked into the kitchen...BAM!...explosion of pots and pans and utensils and all sorts of mess. Alex and her friends had graduated to facebook in the other room. I went in and asked what was up with the kitchen and they all proceeded to shell out 5 bucks. I said...is it just easier to give me 5 bucks than to clean up after yourselves? They all smiled and said "yea, it is." I'm not sure how I'm feeling about this. Is this still an effective parenting strategy? Am I alright with the casualness in which they all just handed over the money? Are they learning what they are supposed to be learning? Am I enabling them? I don't know what to think, but I do know I've never been paid $25.00 before for cleaning my own kitchen.