Since its close to the freezing point here, wearing layers is necessary for biking. on wet days I generate about half a load of laundry of filthy clothes, and i get so gritty i hose myself and my bike down in the yard. With gas being as cheap as it is, my little optimizer voice is wont stop wondering whether biking is saving any money on wet days (on dry days, outer layers can go a few rides between washes, and i can wear a bit less since I'm not soaked). I really don't want to feel so compelled to figure out how much a load of laundry costs - there's no reason I need to know, because it won't change my laundry use.
At least it's a thought that is easily silenced, because I still prefer a rainy bike ride on a chilly day to driving the car.