[From scribbled Moleskine notes made in the 5 hour wait early on Monday morning. Id been up since three.]
If you dont want people to get confused over your mumbled prices and end up having to put things back, you might like to try writing the prices of things ON them. Maybe on a little sticky sticker or something. Just a thought.
May save you the trouble of getting all surly and literally Throwing the products back in your customers faces. Again, just an idea. No pressure.