Dollar is fine, but I give you the change in riel, okay?

I was waiting at a stall in Psar Chas Old Market while a seller counted out coins for a man buying fruit. She said, very seriously, "Dollar is fine, but I give you the change in riel, okay?" He thought about it, said okay, and then asked what a riel was worth. She told him to stop worrying and take the bananas. I wrote it down afterwards because it was the most efficient piece of paperwork I had watched all week, and nobody had to sign anything.