Buy One, Get One Free

At a "Buy one, Get one free" sale in Edgartown, Massachusetts, Marash Girl pondered over her two selections.
The saleswoman approached. "Can I help you?"
Marash Girl: "I can't decide which one I'm buying and which one I'm getting free . . ."
The saleswoman, irritated: "What difference does it make?"
Marash Girl just laughed.