>> Given that the bananas obviously aren't on sale for $0.0019, it seems idiotic to me ignore alternative explanations for the sign.

"It's a banana Michael. What could it cost, 10 dollars?!"

You say "obvious" but I don't think that means what you think that means. Why is it obvious? Why would it be impossible that a store sells bananas at a loss in order to pull people in (what people in sales call a "loss leader")? If you don't buy bananas regularly, why couldn't you assume this is just a great deal?

If there were a sign advertising 5 bananas for a penny (or whatever) with no asterisk, fine print, or mention that "terms may apply", I would be livid if I couldn't take advantage of that price.