Is it cheaper?

I think all of my cheapness lately is rubbing off on Malika.

Yesterday, we went to play at a friends house, and while we were there, Malika had an accident. We had to borrow clothes for her to wear, since I didn't bring any extra. So, on the way home she says, "Is it cheaper to wear these clothes to bed?" I had to ask her twice, because I've never heard her say cheaper. I don't think she understands fully what it means, or maybe she does and she is trying to save a few cents from having to do extra laundry if she wore her pajamas.