I spent about 10-12 hours sewing each costume. With sewing, I find I can do some parts while taking care of the kids. You know how some activities are easy to do while taking care of children and some are not? Also, those activities change with the age of the children... Well, right now, sewing seems to fit well with kid-care.
Mattias's blue clown costume above is still listed on the Etsy store for a small fortune. You can check out all the built-in tricks there.