Whenever I see kids selling lemonade for a charity (or for a new iPad) on a hot Summer day on the bike trail, I want to tell them (or their hovering parents) "You should be selling cold bottled water!" People would have no problem dropping a dollar for a bottle of water that only costs a dime when bought in bulk. They do it all the time when they're out and about these days.
So I find this Girl Scout's ingenuity and entrepreneurial spirit commendable. She will go far in business, if that's the direction she chooses, having learned a good lesson about supply and demand.