I say "Sorry, I don't take requests". Then I sometimes add that it takes a lot of time and effort and supplies to make a quilt and I make lots of donation quilts. Or, I say
"only if you paint a room in my house and it will be lots cheaper for you and you will be finished first." Yikes! That is only for people who barely know me and have no boundaries. I have been asked to make a "custom" cover for fishing poles etc... !