I'm a proud tightwad, so when someone gets 30 cents out of me, it's a life event.
The other day I was at Barnes & Noble in Dublin and after I ordered my small coffee (so cheap!) the barista did something a bit unexpected. She held up small and medium cups next to each other and said this:
"Do you want the medium? It's only 30 cents more."
Guess what I did? I got it.
If you multiply this simple customer interaction (transaction) for that location then consider the thousands of stores, you're suddenly talking about millions more per year in coffee sales. Wow.